SMSC EMC6D102 DATASHEET Revision 0.4 (04-05-05)
Datasheet
PRODUCT FEATURES
EMC6D102
Fan Control Device with
Hardware Monitoring and
Acoustic Noise Reduction
Features
■3.3 Volt Operation (5 Volt Tolerant Input Buffers)
■SMBus 2.0 compliant interface (Fixed, Not
Discoverable) With Three Slave Address Options
■Fan Control
— PWM (Pulse width Modulation) Outputs (3)
— Fan Tachometer Inputs (4)
— Individual status and enable bits per tach input
— Programmable automatic fan control based on
temperature
— Fan ramp rate control for acoustic noise reduction
■Temperature Monitor
— Monitoring of Two Remote Thermal Diodes (+/- 3 deg
C accuracy)
— Internal Ambient Temperature Measurement
— Limit Comparison of all Monitored Values
— Individual status and enable bits per thermal input
— Interrupt Pin for out-of-limit Temperature Indication
— Configurable offset for internal or external temperature
channels.
— Supports 4 programmable temperature averaging
modes
— 2 monitoring modes: Continuous or Cycle (Power
Saving mode)
— Offers 2 Low Power Modes when monitoring is off:
Sleep and Shutdown
■Voltage Monitor
— Monitor Power supplies (+2.5V, +5V, +12V, Vccp, and
VCC)
— Individual status and enable bits per voltage input
— Limit Comparison of all Monitored Values
— Interrupt Pin for out-of-limit Voltage Indication
— Supports 4 programmable voltage averaging modes
— 2 monitoring modes: Continuous or Cycle (Power
Saving mode)
— Offers 2 Low Power Modes when monitoring is off:
Sleep and Shutdown
■5 VID (Voltage Identification) inputs
■XOR Tree test mode
■Mechanical Package (24-pin SSOP); green, lead-free
package also available
ORDER NUMBER(S):
EMC6D102-CK FOR 24 PIN SSOP PACKAGE
EMC6D102-CK-TR FOR 24 PIN SSOP PACKAGE
EMC6D102-CZC FOR 24 PIN SSOP PACKAGE (GREEN, LEAD-FREE)
EMC6D102-CZC-TR FOR 24 PIN SSOP PACKAGE (GREEN, LEAD-FREE)
80 Arkay Drive
Hauppauge, NY 11788
(631) 435-6000
FAX (631) 273-3123
Copyright © SMSC 2005. All rights reserved.
Circuit diagrams and other information relating to SMSC products are included as a means of illustrating typical applications. Consequently,
complete information sufficient for construction purposes is not necessarily given. Although the information has been checked and is believed to be
accurate, no responsibility is assumed for inaccuracies. SMSC reserves the right to make changes to specifications and product descriptions at any
time without notice. Contact your local SMSC sales office to obtain the latest specifications before placing your product order. The provision of this
information does not convey to the purchaser of the described semiconductor devices any licenses under any patent rights or other intellectual
property rights of SMSC or others. All sales are expressly conditional on your agreement to the terms and conditions of the most recently dated
version of SMSC's standard Terms of Sale Agreement dated before the date of your order (the "Terms of Sale Agreement"). The product may
contain design defects or errors known as anomalies which may cause the product's functions to deviate from published specifications. Anomaly
sheets are available upon request. SMSC products are not designed, intended, authorized or warranted for use in any life support or other
application where product failure could cause or contribute to personal injury or severe property damage. Any and all such uses without prior written
approval of an Officer of SMSC and further testing and/or modification will be fully at the risk of the customer. Copies of this document or other
SMSC literature, as well as the Terms of Sale Agreement, may be obtained by visiting SMSC’s website at http://www.smsc.com. SMSC is a
registered trademark of Standard Microsystems Corporation (“SMSC”). Product names and company names are the trademarks of their respective
holders.
SMSC DISCLAIMS AND EXCLUDES ANY AND ALL WARRANTIES, INCLUDING WITHOUT LIMITATION ANY AND ALL IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE, AND AGAINST INFRINGEMENT AND THE LIKE,
AND ANY AND ALL WARRANTIES ARISING FROM ANY COURSE OF DEALING OR USAGE OF TRADE.
IN NO EVENT SHALL SMSC BE LIABLE FOR ANY DIRECT, INCIDENTAL, INDIRECT, SPECIAL, PUNITIVE, OR CONSEQUENTIAL
DAMAGES; OR FOR LOST DATA, PROFITS, SAVINGS OR REVENUES OF ANY KIND; REGARDLESS OF THE FORM OF ACTION,
WHETHER BASED ON CONTRACT; TORT; NEGLIGENCE OF SMSC OR OTHERS; STRICT LIABILITY; BREACH OF WARRANTY; OR
OTHERWISE; WHETHER OR NOT ANY REMEDY OF BUYER IS HELD TO HAVE FAILED OF ITS ESSENTIAL PURPOSE, AND WHETHER
OR NOT SMSC HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Revision 0.4 (04-05-05) 2 SMSC EMC6D102
DATASHEET
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102 3 Revision 0.4 (04-05-05)
DATASHEET
Table of Contents
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Chapter 2 Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 3 Pin Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 Buffer Type Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 3.3V Operation, 5V Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chapter 4 SMBus Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1 Slave Address. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2 Slave Bus Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3 Bus Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.4 Invalid Protocol Response Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.4.1 Undefined Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.5 General Call Address Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.6 Slave Device Time-Out. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.7 Stretching the SCLK Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.8 SMBus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.9 Bus Reset Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.10 SMBus Alert Response Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chapter 5 Hardware Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1 Input Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2 Resetting the EMC6D102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2.2 Soft Reset (Initialization) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3 Monitoring Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3.1 Continuous Monitoring Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.3.2 Cycle Monitoring Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.4 Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.4.1 Diode Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.5 Interrupt Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.6 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.6.1 Sleep Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.6.2 Shutdown Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.7 Analog Voltage Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.8 Voltage ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9 Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9.1 Internal Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9.2 External Temperature Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.9.3 Temperature Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.9.4 Offset Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.10 Thermal Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 6 Fan Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.1.1 Limit and Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.1.2 Device Set-Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.1.3 PWM Fan Speed Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.1.4 Fan Speed Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Revision 0.4 (04-05-05) 4 SMSC EMC6D102
DATASHEET
6.1.5 Linking Fan Tachometers to PWMs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Chapter 7 Register Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
7.1 Undefined Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.2 Defined Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
7.2.1 Register 10h: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
7.2.2 Register 1Dh, 1Eh, 1Fh: Offset Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
7.2.3 Registers 20-24h: Voltage Reading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
7.2.4 Registers 25-27h: Temperature Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.2.5 Registers 28-2Fh: Fan Tachometer Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
7.2.6 Registers 30-32h: Current PWM Duty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
7.2.7 Register 3Eh: Company ID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.2.8 Register 3Fh: Version / Stepping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
7.2.9 Register 40h: Ready/Lock/Start Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
7.2.10 Register 41h: Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
7.2.11 Register 42h: Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
7.2.12 Register 43h: VID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
7.2.13 Registers 44-4Dh: Voltage Limit Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
7.2.14 Registers 4E-53h: Temperature Limit Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
7.2.15 Registers 54-5Bh: Fan Tachometer Low Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
7.2.16 Registers 5C-5Eh: PWM Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
7.2.17 Registers 5F-61h: Zone Temperature Range, PWM Frequency . . . . . . . . . . . . . . . . . . . 60
7.2.18 Register 62h, 63h: Min/Off, PWM Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . 62
7.2.19 Registers 64-66h: Minimum PWM Duty Cycle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
7.2.20 Registers 67-69h: Zone Low Temperature Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
7.2.21 Registers 6A-6Ch: Absolute Temperature Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
7.2.22 Registers 6D-6Eh: Zone Hysteresis Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
7.2.23 Register 6F: XOR Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.2.24 Register 79h: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.2.25 Register 7Ah: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.2.26 Register 7Bh: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
7.2.27 Register 7Ch: Special Function Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
7.2.28 Register 7Eh: Interrupt Enable 1 Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
7.2.29 Register 7Fh: Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
7.2.30 Register 80h: Interrupt Enable 2 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
7.2.31 Register 81h: TACH_PWM Association Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7.2.32 Register 82h: Interrupt Enable 3 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
7.2.33 Registers 85h-88h: A/D Converter LSbs Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
7.2.34 Register 89h: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.35 Registers 8Ah: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.36 Registers 8Bh: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.37 Registers 8Ch: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.38 Registers 8Dh: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.39 Registers 8Eh: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
7.2.40 Registers 90h-93h: TachX Option Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
7.2.41 Registers 94h-96h: PWMx Option Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
7.2.42 Register 97h: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
7.2.43 Register 98h:SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
7.2.44 Register FFh: SMSC Test Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Chapter 8 Operational Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
8.1 Maximum Guaranteed Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
8.2 Ratings for Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Chapter 9 Timing Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102 5 Revision 0.4 (04-05-05)
DATASHEET
9.1 PWM Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
9.2 SMBus Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Chapter 10 Mechanical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Appendix A ADC Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Appendix B Example Fan Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Revision 0.4 (04-05-05) 6 SMSC EMC6D102
DATASHEET
List of Figures
Figure 2.1 EMC6D102 Pin Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 4.1 Address Selection on EMC6D102 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 5.1 Interrupt Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 6.1 Automatic Fan Control Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Figure 6.2 Automatic Fan Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 6.3 Spin Up Reduction Enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Figure 6.4 Illustration of PWM Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Figure 6.5 PWM and Tachometer Concept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Figure 7.1 Fan Activity Above Fan Temp Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Figure 9.1 PWMx Output Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Figure 9.2 SMBus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Figure 10.1 24-Pin SSOP Package Outline, 0.150 Wide Body, 0.025 Pitch . . . . . . . . . . . . . . . . . . . . . . . 82
Figure B.1 Fan Drive Circuitry (Apply to PWM Driving Two Fans) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Figure B.2 Fan Drive Circuitry (Apply to PWM Driving One Fan) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
Figure B.3 Fan Tachometer Circuitry (Apply to Each Fan) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Figure B.4 Remote Diode (Apply to Remote2 Lines). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Figure B.5 Suggested Minimum Track Width and Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
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Datasheet
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DATASHEET
List of Tables
Table 3.1 EMC6D102 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Table 3.2 Buffer Type Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Table 4.1 SMBus Slave Address Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 4.2 SMBus Write Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 4.3 SMBus Read Byte Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Table 4.4 Modified SMBus Receive Byte Protocol Response to ARA. . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 5.1 AVG[2:0] Bit Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 5.2 Conversion Cycle Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 5.3 ADC Conversion Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Table 5.4 Low Power Mode Control Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 5.5 Min/Max ADC Conversion Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 5.6 Temperature Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 6.1 PWM Ramp Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Table 6.2 Max Tachometer Count Values for Different Stretch Periods . . . . . . . . . . . . . . . . . . . . . . . . . 41
Table 6.3 Minimum RPM Detectable Using 3 Edges – No PWM Stretching . . . . . . . . . . . . . . . . . . . . . . 41
Table 6.4 Minimum RPM Detectable Using 2 Edges – No PWM Stretching . . . . . . . . . . . . . . . . . . . . . . 42
Table 6.5 Minimum RPM Detectable– With PWM Stretching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Table 7.1 Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Table 7.2 Voltage vs. Register Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Table 7.3 Temperature vs. Register Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Table 7.4 PWM Duty vs Register Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Table 7.6 Temperature Limits vs. Register Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Table 7.7 Fan Zone Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Table 7.8 Fan Spin-Up Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Table 7.9 Register Setting vs. PWM Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Table 7.10 Register Setting vs. Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Table 7.11 PWM output below Limit depending on value of Off/Min . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Table 7.12 PWM Ramp Rate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Table 7.13 PWM Duty vs. Register Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Table 7.14 Temperature Limit vs. Register Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Table 7.15 Absolute Limit vs. Register Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Table 7.16 Hysteresis Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Table 7.17 AVG[2:0] Bit Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Table 9.1 Timing for PWM[1:3] Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Table 10.1 24-pin SSOP Package Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Table A.1 Analog-to-Digital Voltage Conversions for Hardware Monitoring Block. . . . . . . . . . . . . . . . . . 83
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Revision 0.4 (04-05-05) 8 SMSC EMC6D102
DATASHEET
Chapter 1 General Description
The EMC6D102 is an environmental monitoring device with automatic fan control capability. This ACPI
compliant device provides hardware monitoring for up to five voltages and three thermal zones,
measures the speed of up to four fans, and controls the speed of multiple DC fans using Pulse Width
Modulator (PWM) outputs.
The EMC6D102 hardware monitor provides analog inputs for monitoring external voltages of +2.5V,
+5V, +12V and Vccp. This device has the capability to monitor its own internal VCC power supply,
which may be connected to either main power (VCC) or the suspend power well (VTR). In addition to
monitoring the processor voltage, VID inputs are available to identify the voltage specification. External
components are not required for voltage scaling or similar treatment.
The EMC6D102 hardware monitor includes support for monitoring three thermal zones: two external
and one internal. The external temperatures are measured via thermal diode inputs capable of
monitoring remote devices. In addition, they are equipped with an ambient temperature sensor for
measuring the internal temperature.
Pulse Width Modulators (PWM) control the speed of the fans by varying the output duty cycle of the
PWM. Each PWM can be associated with any or all of the thermal zones monitored. As the
temperature of the associated zone varies, the PWM duty cycle is adjusted accordingly. The Ramp
Rate Control feature controls the rate of change of the PWM output, thereby reducing system noise
created by changing the fan speed. The speed of each fan is monitored by a Fan Tachometer input.
The measured values are compared to values stored in Limit Registers to detect if a fan has stalled
or seized.
Fan speed may be under host software control or automatic. In host control mode, the host software
continuously monitors temperature and fan speed registers, makes decisions as to desired fan speed
and sets the PWM’s to drive the required fan speed. This device offers an interrupt output signal
(INT#), which may be used to interrupt the host on out-of-limit temperature or voltage condition
enabling an ACPI response as opposed to the host software continuously monitoring status. In auto
“zone” mode, the logic continuously monitors the temperature and fan speeds and adjusts speeds
without intervention from the host CPU. Fan speed is adjusted according to an algorithm using the
temperature measured in the selected zone, the high and low limits set by the user, and the current
fan speed.
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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DATASHEET
Chapter 2 Pinout
This Environmental Monitoring and Control device (EMC) is offered in a 24 pin SSOP mechanical
package.
The EMC6D102 is a 24 pin SSOP.
Figure 2.1 EMC6D102 Pin Diagram
24
23
22
21
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
9
10
11
12
SDA
SCL
VSS
VCC
VID0
VID1
VID2
VID3
VID4
TACH3/INT#
PWM2/INT#
TACH1
TACH2
PWM1/xTest Out
Vccp
2.5V
12V
5V
Remote1+
Remote1-
Remote2+
Remote2-
TACH4/Address Select
PWM3/Address Enable
EMC6D102
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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Chapter 3 Pin Description
3.1 Pin Functions
Table 3.1 EMC6D102 Pin Description
NAME FUNCTION
BUFFER
TYPE
BUFFER
REQUIREMENT
PER FUNCTION
(Note 3.1)
POWER
WELL NOTES
HARDWARE MONITORING BLOCK (24)
SDA System Management Bus bi-directional Data.
Open Drain output.
IMOD3 IMOD3 VCC
SCLK System Management Bus Clock. IMIMVCC
VID0 Voltage ID 0 Input IMIMVCC
VID1 Voltage ID 1 Input IMIMVCC
VID2 Voltage ID 2 Input IMIMVCC
VID3 Voltage ID 3 Input IMIMVCC
VID4 Voltage ID 4 Input IMIMVCC
Remote1- This is the negative Analog input (current
sink) from the remote thermal diode. This
serves as the negative input into the A/D.
Digital Input.
IAN IAN VCC
Remote1+ This is the positive input (current source)
from the remote thermal diode. This serves
as the positive input into the A/D.
IAN IAN VCC
Remote2- This is the negative Analog input (current
sink) from the remote thermal diode. This
serves as the negative input into the A/D.
Digital Input.
IAN IAN VCC
Remote2+ This is the positive input (current source)
from the remote thermal diode. This serves
as the positive input into the A/D.
IAN IAN VCC
+5V_IN Analog input for +5V IAN IAN VCC Note 3.2
+2.5V_IN Analog input for +2.5V IAN IAN VCC Note 3.2
Vccp Analog input for +Vccp (processor voltage: 0
to 3.0V).
IAN IAN VCC Note 3.2
12V_IN Analog input for +12V IAN IAN VCC Note 3.2
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Note: The “#” as the suffix of a signal name indicates an “Active Low” signal.
Note 3.1 Buffer types per function on multiplexed pins are separated by a slash “/”. Buffer types in
parenthesis represent multiple buffer types for a single pin function.
Note 3.2 This analog input is backdrive protected.
3.2 Buffer Type Description
Note: The buffer type values are specified at VCC=3.3V
TACH1 Input for monitoring a fan tachometer input. IMIMVCC
TACH2 Input for monitoring a fan tachometer input. IMIMVCC
TACH3
/INT#
Input for monitoring a fan tachometer input.
/Interrupt output to indicate a thermal and/or
voltage event.
IMOD3 IM /OD3 VCC
TACH4
/Address
Select
Input for monitoring a fan tachometer input.
If in Address Select Mode, determines the
SMBus address of the device.
IMIMVCC
PWM1
/xTest Out
PWM Output 1 controlling speed of fan.
When in XOR tree test mode, functions as
XOR Tree output.
O8 OD8/O8 VCC
PWM2
/INT#
PWM Output 2 controlling speed of fan.
/Interrupt output to indicate a thermal and/or
voltage event.
OD8 OD8/OD8 VCC
PWM3
/Address
Enable#
PWM Output 3 controlling speed of fan.
If pulled to ground at power on, enables
Address Select Mode (Address Select pin
controls SMBus address of the device).
IOD8 OD8/I VCC
VCC Positive Power Supply. Nominal 3.3V.
VCC is monitored by the Hardware
Monitoring Block.
(Can be powered by +3.3V Standby power if
monitoring in low power states is required.)
VSS Analog Ground.
Table 3.2 Buffer Type Descriptions
BUFFER TYPE DESCRIPTION
IMDigital Input
IAN Analog Input, Hardware Monitoring Block.
IMOD3 Input/Output (Open Drain), 3mA sink.
O8 Output, 8mA sink, 4mA source.
OD8 Output (Open Drain), 8mA sink.
IO8 Input/Output, 8mA sink, 4mA source.
Table 3.1 EMC6D102 Pin Description (continued)
NAME FUNCTION
BUFFER
TYPE
BUFFER
REQUIREMENT
PER FUNCTION
(Note 3.1)
POWER
WELL NOTES
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3.3 3.3V Operation, 5V Tolerance
The EMC6D102 is intended to operate with a nominal 3.3V power supply. The analog voltage pins are
connected to voltage sources at their respective nominal levels. All digital signal pins are 3V switching,
but are tolerant to 5V.
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Chapter 4 SMBus Interface
The host processor communicates with the Fan Monitoring device through a series of read/write
registers via the SMBus interface. SMBus is a serial communication protocol between a computer host
and its peripheral devices.
4.1 Slave Address
The default Slave Address is 0101110b. If this address is desired, the designer should not ground the
Address Enable# pin and should not apply a strapping resistor to the Address Select pin.
If multiple devices are implemented in a system or another SMBus device requires address 0101110b,
TACH4 and PWM3 must be disabled. In this case, addressing is implemented as follows:
The board designer will apply a 10KΩ pull-down resistor to ground on the Address Enable# pin. Upon
power up, the EMC6D102 device will be placed into Address Enable mode and assign itself an SMBus
address according to the Address Select input. The device will latch the address during the first valid
SMBus transaction in which the first five bits of the targeted address match those of the EMC6D102
address. This feature eliminates the possibility of a glitch on the SMBus interfering with address
selection.
In this way, there can be up to three EMC6D102 devices on the SMBus at any time. Multiple
EMC6D102 devices can be used to monitor additional processors and temperature zones.
Table 4.1 SMBus Slave Address Options
ADDRESS
ENABLE#
ADDRESS
SELECT BOARD IMPLEMENTATION SMBUS ADDRESS [7:1]
1 X Address Enable# pulled to VCC through resistor
Note: Resistor value will be dependent on PWM
circuit implemented.
0101 110b
(default)
0 0 Address Enable# pulled to ground through 10kΩ
resistor
Address Select Pulled to ground through a 10kΩ
resistor
0101 100b
0 1 Address Enable# pulled to ground through 10kΩ
resistor
Address Select pulled to VCC through a 10kΩ
resistor
0101 101b
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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Figure 4.1 Address Selection on EMC6D102
4.2 Slave Bus Interface
The EMC6D102 device SMBus implementation is a subset of the SMBus interface to the host. The
device is a slave-only SMBus device. The implementation in the device is a subset of SMBus since it
only supports four protocols.
The Write Byte and Read Byte protocols are valid SMBus protocols for the device. This part responds
to other protocols as described in the Invalid Protocol Section. Reference the System Management
Bus Specification, Rev 2.0.
The SMBus interface is used to read and write the registers in the device. The register set is shown
in section 11 Register Set on page 31.
4.3 Bus Protocols
Typical Write Byte and Read Byte protocols are shown below. Register accesses are performed using
7-bit slave addressing, an 8-bit register address field, and an 8-bit data field. The shading indicates
the Hardware Monitor Block driving data on the SDA line; otherwise, host data is on the SDA line.
The slave address is the unique SMBus Interface Address for the Hardware Monitor Block that
identifies it on SMBus. The register address field is the internal address of the register to be accessed.
The register data field is the data that the host is attempting to write to the register or the contents of
the register that the host is attempting to read.
Note: Data bytes are transferred MSB first.
Byte Protocols
A write byte transfer will always consist of three bytes of information being transferred: the SMBus
Interface Address byte, followed by the Internal Address Register byte, and finally the data byte. A
read byte consists of four bytes of information being transferred. The first three bytes are written by
the host device and the last byte is the byte returned by the hardware monitoring block. The bytes of
information being transferred during a read byte command are: the SMBus Interface Address byte,
followed by the Internal Address Register byte, a repeated SMBus Interface Address byte, and finally
the data byte.
Note: The SMBus controller detects the repeated START condition that is generated before the
repeated SMBus Interface Address byte to distinguish between a write byte protocol and a read
byte protocol. See the following sections for a more detailed description of each of these
protocols.
Start
SDA
SCL
Address Decided
First five address bits
0 1 0 1 1
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Write Byte
The Write Byte protocol is used to write data to the registers. The data will only be written if the protocol
shown in Table 4.2 is performed correctly. Only one byte is transferred at time for a Write Byte protocol.
Read Byte
The Read Byte protocol is used to read data from the registers. The data will only be read if the
protocol shown in Ta b le 4. 3 is performed correctly. Only one byte is transferred at time for a Read Byte
protocol.
4.4 Invalid Protocol Response Behavior
Registers that are accessed with an invalid protocol will not be updated. A register will only be updated
following a valid protocol. The only valid protocols are the Write Byte and Read Byte protocols, which
are described above.
The EMC6D102 device responds to three SMBus slave addresses:
1. The SMBus slave address that supports the valid protocols defined in the previous sections is
determined by the level on the Address Select and Address Enable pins as shown in Section 4.1,
"Slave Address," on page 13.
2. SMBus Alert Response (0001 100). The SMBus will only respond to the SMBus Alert Response
Address if the SMBus Alert Response interrupt was generated to request a response from the Host.
The SMBus Alert Response is defined in Section 4.10, "SMBus Alert Response Address," on
page 16.
Attempting to communicate with the Hardware Monitor Block over SMBus with an invalid slave
address, or invalid protocol will result in no response, and the SMBus Slave Interface will return to the
idle state.
The only valid registers that are accessible by the SMBus slave address are the registers defined in
the Registers Section. See Section 4.4.1, "Undefined Registers" for response to undefined registers.
4.4.1 Undefined Registers
Reads to undefined registers return 00h. Writes to undefined registers have no effect and return no
error.
4.5 General Call Address Response
The EMC6D102 will not respond to a general call address of 0000_000.
Table 4.2 SMBus Write Byte Protocol
FIELD START SLAVE ADDR WR ACK REG. ADDR ACK REG. DATA ACK STOP
Bits 171181811
Table 4.3 SMBus Read Byte Protocol
FIELD: START
SLAVE
ADDR WR ACK
REG.
ADDR ACK START
SLAVE
ADDR RD ACK
REG.
DATA NACK STOP
Bits: 1711811711811
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4.6 Slave Device Time-Out
The EMC6D102 supports the slave device timeout as per the SMBus Specification, v2.0.
According to SMBus specification, v2.0 devices in a transfer can abort the transfer in progress and
release the bus when any single clock low interval exceeds 25ms (TTIMEOUT, MIN). Devices that have
detected this condition must reset their communication and be able to receive a new START condition
no later than 35ms (TTIMEOUT, MAX).
Note: Some simple devices do not contain a clock low drive circuit; this simple kind of device typically
may reset its communications port after a start or stop condition
4.7 Stretching the SCLK Signal
The EMC6D102 supports stretching of the SCLK by other devices on the SMBus. The Hardware
Monitor Block does not stretch the SCLK.
4.8 SMBus Timing
The SMBus Slave Interface complies with the SMBus AC Timing Specification. See the SMBus timing
diagram shown in the section titled Section 9.2, "SMBus Interface," on page 80.
4.9 Bus Reset Sequence
The SMBus Slave Interface will reset and return to the idle state upon a START field followed
immediately by a STOP field.
4.10 SMBus Alert Response Address
The EMC6D102 device responds to the SMBus Alert Response Address, 0001 100, if the INTEN bit
(register 7Ch bit 2) is set and one or more status events bits are high. The interrupt signal (INT#),
which can be enabled on either the PWM2 or TACH3 pins, can be used as the SMBALERT#. See the
section describing the Interrupt Status Registers on page 21 and the section describing the Interrupt
Pin on page 23 for more details on interrupts.
The device can signal the host that it wants to talk by pulling the SMBALERT# low, if a status bit is
set in one of the interrupt status registers and properly enabled onto the INT# pin. The host processes
the interrupt and simultaneously accesses all SMBALERT# devices through a modified Receive Byte
operation with the Alert Response Address (ARA).
The EMC6D102 device, which pulled SMBALERT# low, will acknowledge the Alert Response Address
and respond with its device address. The 7-bit device address provided by the EMC6D102 device is
placed in the 7 most significant bits of the byte. The eighth bit can be a zero or one.
After acknowledging the slave address, the EMC6D102 device will disengage the SMBALERT# pull-
down by clearing the INT enable bit. If the condition that caused the interrupt remains, the Fan Control
device will reassert the SMBALERT# on the next monitoring cycle, provided the INT enable bit has
been set back to ‘1’ by software.
Table 4.4 Modified SMBus Receive Byte Protocol Response to ARA
FIELD: START
ALERT
RESPONSE
ADDRESS RD ACK
EMC6D102 SLAVE
ADDRESS NACK STOP
Bits: 1711 8 11
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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Note: The INT# signal is an alternate function on the PWM2 and TACH3 pins. The EMC6D102 device
will respond to the SMBus Alert Response address even if the INT# signal is not selected as
the alternate function on one of these pins as long as the following conditions exist: the INTEN
bit (register 7Ch bit 2) is set, an individual status bit is set in one of the interrupt status
registers, and the corresponding group enable bit is set. Each interrupt event must be enabled
into the interrupt status registers, and the status bits must be enabled onto the INT# signal via
the group enable bits for each type of event (i.e., temperature, voltage and fan). See the
section titled Interrupt Status Registers on page 21.
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Chapter 5 Hardware Monitoring
The following sub-sections describe the EMC6D102 Hardware Monitoring features.
5.1 Input Monitoring
The EMC6D102 device’s monitoring function is started by writing a ‘1’ to the START bit in the
Ready/Lock/Start Register (0x40). Measured values from the analog inputs and temperature sensors
are stored in Reading Registers. The values in the reading registers can be accessed via the SMBus
interface. These values are compared to the programmed limits in the Limit Register. The out-of-limit
and diode fault conditions are stored in the Interrupt Status Registers.
5.2 Resetting the EMC6D102
5.2.1 Power-On Reset
All the registers in the Hardware Monitor Block, except the reading registers, reset to a default value
when power is applied to the block. The default state of the register is shown in the table in the
Register Summary subsection. The default state of Reading Registers are not shown because these
registers have indeterminate power on values.
Note: Usually the first action after power up is to write limits into the Limit Registers.
5.2.2 Soft Reset (Initialization)
Setting bit 7 of the CONF register performs a soft reset. This bit is self-clearing. Soft Reset performs
reset on all the registers except the Reading Registers.
5.3 Monitoring Modes
The Hardware Monitor Block supports two Monitoring modes: Continuous Mode and Cycle Mode.
These modes are selected using bit 1 of the Special Function Register (7Ch). The following
subsections contain a description of these monitoring modes.
The hardware monitor conversion clock is 45KHz ± 10%. Temperature conversions take 96 clocks,
each (2.133ms nom.); voltage conversions take 68 clocks, each (1.511ms nom). The time to complete
a conversion cycle depends upon the number of inputs in the conversion sequence to be measured
(see Table 5.3, “ADC Conversion Sequence,” on page 20) and the amount of averaging per input,
which is selected using the AVG[2:0] bits in the Special Function register (see on page 68).
For each mode, there are four options for the number of measurements that are averaged for each
temperature and voltage reading. These options are selected using bits[7:5] of the Special Function
register (7Ch). These bits are defined as follows:
Bits [7:5] AVG[2:0]
The AVG[2:0] bits determine the amount of averaging for each of the measurements that are performed
by the hardware monitor before the reading registers are updated (Ta b le 5. 1 ). The AVG[2:0] bits are
priority encoded where the most significant bit has highest priority. For example, when the AVG2 bit
is asserted, 32 averages will be performed for each measurement before the reading registers are
updated regardless of the state of the AVG[1:0] bits.
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Note: The default for the AVG[2:0] bits is ‘010’b.
To calculate conversion cycle timing for a given averaging mode:
■Compute total number of temperature conversions (TEMP_CONV)
■Compute total number of voltage conversions (VOLT_CONV)
■Calculate Time to complete all conversions is:
Total Conversion Time = (TEMP_CONV)*96/(45kHz +/-10%)+ (VOLT_CONV)*68/(45kHz +/-10%)
Example: To calculate the nominal conversion time FOR AVG[2:0] = 001b.
Total Conversion Time = (TEMP_CONV)*96/(45kHz)+ (VOLT_CONV)*68/(45kHz)
Total Conversion Time = (16+16+1)*96/(45kHz)+ (5*1)*68/(45kHz)
Total Conversion Time = (33)*2.133ms+ (5)*1.511ms = ~78ms
Table 5.2 illustrates the min., nom., and max. conversion cycle timing for each of the four averaging
modes.
Notes:
■The hardware monitor conversion clock is 45KHz ± 10%.
■Temperature conversions take 96 clocks, each (2.133ms nom.); Voltage conversions take 68
clocks, each (1.511ms nom).
5.3.1 Continuous Monitoring Mode
In the continuous monitoring mode, the sampling and conversion process is performed continuously
for each voltage and temperature reading after the Start bit is set high. The time for each voltage and
temperature reading is shown above for each measurement option.
Table 5.1 AVG[2:0] Bit Decoder
SFTR[7:5] MEASUREMENTS PER READING
AVG2 AVG1 AVG0
REMOTE
DIODE 1
REMOTE
DIODE 2
INTERNAL
DIODE
ALL VOLTAGE READINGS
(+2.5V, +5V, +12V, VCCP, AND VCC)
000 128 128 8 8
0 0 1 16 16 1 1
01X161616 16
1XX323232 32
Table 5.2 Conversion Cycle Timing
AVG[2:0]
TOTAL
TEMPERATURE
CONVERSIONS
TOTAL
VOLTAGE
CONVERSIONS
CONVERSION CYCLE TIME (MSEC)
MIN. NOM. MAX.
000 (2x128)+(1x8)=264 5x8=40 567 624 693
001 (2x16)+(1x1)=33 5x1=5 71 78 87
01X (default) 3x16=48 5x16=80 203 223 248
1XX 3x32=96 5x32=160 406 447 496
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The continuous monitoring function is started by doing a write to the Ready/Lock/Start Register, setting
the Start bit (Bit 0) high. The part then performs a “round robin” sampling of the inputs, in the order
shown below (see Tab l e 5 . 3 ). Sampling of all values occurs in a nominal 223 ms (default - see
Table 5.2, “Conversion Cycle Timing,” on page 19).
When the continuous monitoring function is started, it cycles through each measurement in sequence,
and it continuously loops through the sequence approximately once every 223 ms (default - see
Table 5.2, “Conversion Cycle Timing,” on page 19). Each measured value is compared to values stored
in the Limit registers. When the measured value violates the programmed limit the Hardware Monitor
Block will set a corresponding status bit in the Interrupt Status Registers.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See Auto
Fan Control Operating Mode on page 30.
The results of the sampling and conversions can be found in the Reading Registers and are available
at any time.
5.3.2 Cycle Monitoring Mode
In cycle monitoring mode, the part completes all sampling and conversions, then waits approximately
one second to repeat the process. It repeats the sampling and conversion process typically every 1.2
seconds (1.4 sec max - default averaging enabled). The sampling and conversion of each voltage and
temperature reading is performed once every monitoring cycle. This is a power saving mode.
The cycle monitoring function is started by doing a write to the Ready/Lock/Start Register, setting the
Start bit (Bit 0) high. The part then performs a “round robin” sampling of the inputs, in the order shown
above.
When the cycle monitoring function is started, it cycles through each measurement in sequence, and
it produces a converted voltage and temperature reading for each input. The state machine waits
approximately one second before repeating this process. Each measured value is compared to values
stored in the Limit registers. When the measured value violates (or is equal to) the programmed limit
the Hardware Monitor Block will set a corresponding status bit in the Interrupt Status Registers.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See the
section titled Auto Fan Control Operating Mode on page 30.
The results of each sampling and conversion can be found in the Reading Registers and are available
at any time, however, they are only updated once per conversion cycle.
Table 5.3 ADC Conversion Sequence
SAMPLING ORDER REGISTER
1 Remote Diode Temp Reading 1
2 Ambient Temperature reading
3 VCC reading
4 +12V reading
5+5V reading
6 +2.5V reading
7 Vccp (processor) reading
8 Remote Diode Temp Reading 2
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5.4 Interrupt Status Registers
The Hardware Monitor Block contains two interrupt status registers: Register 41h: Interrupt Status
Register 1 on page 54 and on page 55. These registers are used to reflect the state of all temperature,
voltage and fan violation of limit error conditions and diode fault conditions that the Hardware Monitor
Block monitors.
When an error occurs during the conversion cycle, its corresponding bit is set in its respective interrupt
status register. The bit remains set until the register is read by software, at which time the bit will be
cleared to ‘0’ if the associated error event no longer violates the limit conditions or if the diode fault
condition no longer exists. Reading the register will not cause a bit to be cleared if the source of the
status bit remains active.
These registers are read only – a write to these registers have no effect. These registers default to
0x00 on VCC POR and Initialization.
See the description of the Interrupt Status registers in Chapter 7, "Register Set," on page 45.
Each interrupt status bit has a corresponding bit located in an interrupt enable register, which may be
used to enable/disable the individual event from setting the status bit. See the figure below for the
status and enable bits used to control the interrupt bits and INT# pin.
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Figure 5.1 Interrupt Control
Note: The diode fault bits are not mapped directly to the INT# pin. A diode fault condition forces the
diode reading register to a value of 80h, which will generate a Diode Error condition. See
section Diode Fault on page 22
5.4.1 Diode Fault
The EMC6D102 Chip automatically sets the associated diode fault bit to 1 when any of the following
conditions occur on the Remote Diode pins:
■The positive and negative terminal are an open circuit.
■Positive terminal is connected to VCC
■Positive terminal is connected to ground
■Negative terminal is connected to VCC
INT_STS1 Reg
12V_Error (INT2[0])
Diode 2 Fault (INT2[7])
Diode 1_En (IER3[2])
Diode 2_En (IER3[3])
Diode 1 Fault (INT2[6])
INT2 (INT1[7])
INT_STS2 Reg
Diode 1 Fault
12V_Error_En (IER1[6])
12V_Error
Diode 2 Fault
2.5V_Error (INT1[0])
2.5V_Error_En (IER1[2])
2.5V_Error
Vccp_Error (INT1[1])
Vccp_Error_En (IER1[3])
Vccp_Error
VCC_Error (INT1[2])
VCC_Error_En (IER1[7])
VCC_Error
5V_Error (INT1[3])
5V_Error_En (IER1[5])
5V_Error
Diode 1 Limit (INT1[4])
Diode 1_En (IER3[2])
Diode 1 Limit
Diode 2 Limit (INT1[6])
Diode 2_En (IER3[3])
Diode 2 Limit
Ambient Limit Ambient Limit (INT1[5])
Ambient_En (IER3[1])
TACH1 (INT2[2])
TACH1_En (IER2[1])
TACH1 Out-of-Limit
TACH2 (INT2[3])
TACH2 _En (IER2[2])
TACH2 Out-of-Limit
TACH3 (INT2[4])
TACH3 _En (IER2[3])
TACH3 Out-of-Limit
TACH4 (INT2[5])
TACH4 _En (IER2[4])
TACH4 Out-of-Limit
+
TACH_EN
(IER2[0])
VOLTAGE_EN
(IER1[0])
TEMP_EN
(IER3[0])
+
+
+
INT#
INT_EN
(SFTR[2])
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■Negative terminal is connected to ground
The occurrence of a fault will cause 80h to be loaded into the associated reading register, except for
the case when the negative terminal is connected to ground. A temperature reading of 80h will cause
the corresponding diode error bit to be set. This will cause the INT# pin to become active if the
individual, group (TEMP), and global enable (INTEN) bits are set.
Notes:
■The individual remote diode enable bits and the TEMP bit are located in on page 69. The INTEN
bit is located in bit[2] of on page 68.
■When 80h is loaded into the Remote Diode Reading Register the PWM output(s) controlled by the
zone associated with that diode input will be forced to full on. See Thermal Zones on page 27.
If the diode is disabled, the fault bit in the interrupt status register will not be set. In this case, the
occurrence of a fault will cause 00h to be loaded into the associated reading register. The limits must
be programmed accordingly to prevent unwanted fan speed changes based on this temperature
reading. If the diode is disabled and a fault condition does not exist on the diode pins, then the
associated reading register will contain a “valid” reading.
5.5 Interrupt Pin
The INT# function is used as an interrupt output for out-of-limit temperature, voltage events, and/or fan
errors.
■The INT# signal can be enabled onto the PWM2 or the TACH3 pins.
To configure the PWM2/INT# pin for the interrupt function, set bit[1] P2INT of the CONF register
(7Fh) to ‘1’
To configure the TACH3/INT# pin for the interrupt function, set bit[0] T3INT of the CONF register
(7Fh) to ‘1’
■To enable the interrupt pin to go active, set bit 2 of the Special Function Register (7Ch) to ‘1’.
To enable temperature event, voltage events and/or fan events onto the INT# pin:
■To enable out-of-limit temperature events set bit[0] of the Interrupt Enable 3 (TEMP) register (82h)
to ‘1’.
■To enable out-of-limit voltage events set bit[0] of the Interrupt Enable 1(VOLT) register (7Eh) to ‘1’
■To enable Fan tachometer error events set bit[0] of the Interrupt Enable 2(Fan Tachs) register (80h)
to ‘1’.
See Figure 5.1 on page 22. The following description assumes that the interrupt enable bits for all
events are set to enable the interrupt status bits to be set.
If the internal or remote temperature reading violates the low or high temperature limits, INT# will be
forced active low (if all the corresponding enable bits are set: individual enable bits (D1_EN, D2_EN,
and/or AMB_EN), group enable bit (TEMP_EN) and the global enable bit (INTEN)). This pin will remain
low while the Internal Temp Error bit or one or both of the Remote Temp Error bits in Interrupt Status
1 Register is set and the enable bit is set.
The INT# pin will not become active low as a result of the remote diode fault bits becoming set.
However, the occurrence of a fault will cause 80h to be loaded into the associated reading register,
which will cause the corresponding diode error bit to be set. This will cause the INT# pin to become
active if enabled.
The INT# pin can be enabled to indicate out-of-limit voltages. Bit[0] of the Interrupt Enable 1(VOLT)
register (7Eh) is used to enable this option. When this bit is set, if one or more of the voltage readings
violates the low or high limits, INT# will be forced active low (if all the corresponding enable bits are
set: individual enable bits (VCC_Error_En, 12V_Error_En, 5V_Error_En, 33V_Error_En,
VCCP_Error_En, 25V_Error_En, 18V_Error_En, and/or 15V_Error_En), group enable (VOLT_EN), and
global enable (INT_EN)). This pin will remain low while the associated voltage error bit in the Interrupt
Status Register 1 or Interrupt Status Register 2 is set.
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The INT# pin can be enabled to indicate fan errors. Bit[0] of the Interrupt Enable 2(Fan Tachs) register
(80h) is used to enable this option. This pin will remain low while the associated fan error bit in the
Interrupt Status Register 2 is set.
The INT# pin will remain low while any bit is set in any of the Interrupt Status Registers. Reading the
interrupt status registers will cause the logic to attempt to clear the status bits; however, the status bits
will not clear if the interrupt stimulus is still active. The interrupt enable bit (Special Function Register
bit[2]) should be cleared by software before reading the interrupt status registers to insure that the INT#
pin will be re-asserted while an interrupt event is active, when the INT_EN bit is written to ‘1’ again.
The INT# pin can also be deasserted by issuing an Alert Response Address Call. See the description
in the section titled SMBus Alert Response Address on page 16.
The INT# pin may only become active while the monitor block is operational.
5.6 Low Power Modes
The Hardware Monitor Block can be placed in a low-power mode by writing a ‘0’ to Bit[0] of the
Ready/Lock/Start Register (0x40). The low power mode that is entered is either sleep mode or
shutdown mode as selected using Bit[0] of the Special Function Register (7Ch). These modes do not
reset any of the registers of the Hardware Monitor Block. In both of these modes, the PWM pins are
at 100% duty cycle.
Notes:
■START and LPMD bits cannot be modified when the LOCK bit is set.
■START bit is located in the Ready/Lock/Start register (40h). LPMD bit is located in the Special
Function Register (7Ch)
5.6.1 Sleep Mode
This is a low power mode in which bias currents are on and the internal oscillator is on, but the the
A/D converter and monitoring cycle are turned off. Serial bus communication is still possible with any
register in the Hardware Monitor Block while in this low-power mode.
5.6.2 Shutdown Mode
This is a low power mode in which bias currents are off, the internal oscillator is off, and the the A/D
converter and monitoring cycle are turned off. Serial communication is only possible with Bits[2:0] of
the Special Function Register at 7Ch and Bits [7:0] of the Configuration Register at 7Fh, which become
write-only registers in this mode.
5.7 Analog Voltage Measurement
The Hardware Monitor Block contains inputs for directly monitoring the power supplies (+12 V, +5 V,
+2.5V, +Vccp, and VCC). These inputs are scaled internally to an internal reference source, converted
via an 8 bit successive approximation register ADC or a Delta-Sigma ADC (Analog-to-Digital
Converter), and scaled such that the correct value refers to 3/4 scale or 192 decimal (except the Vccp
input). This removes the need for external resistor dividers and allows for a more accurate means of
measurement since the voltages are referenced to a known value. Since any of these inputs can be
above VCC or below Ground, they are not diode protected to the power rails. The measured values
Table 5.4 Low Power Mode Control Bits
START LPMD DESCRIPTION
0 0 Sleep Mode
0 1 Shutdown Mode
1 x Monitoring
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are stored in the Reading registers and compared with the Limit registers. The status bits in the
Interrupt Status Register 1 and 2 are set if the measured values violate the programmed limits.
The Vccp voltage input measures the processor voltage, which will lie in the range of 0V to 3.0V.
The following table shows the values of the analog inputs that correspond to the min and max output
codes of the A/D converter. For a complete list of the ADC conversions see Appendix A, "ADC Voltage
Conversion," on page 83.
5.8 Voltage ID
VID0-VID4 digital inputs are used to store processor Voltage ID codes (for processor operating voltage)
in the VID0-4 register (43h). These VIDs can be read out by the management system using the SMBus
interface.
5.9 Temperature Measurement
Temperatures are measured internally by bandgap temperature sensor and externally using two sets
of diode sensor pins (for measuring two external temperatures). See subsections below.
Note: The temperature sensing circuitry for the two remote diode sensors is calibrated for a 3904
type diode.
5.9.1 Internal Temperature Measurement
Internal temperature can be measured by bandgap temperature sensor. The measurement is
converted into digital format by internal ADC. This data is converted in two’s complement format since
both negative and positive temperature can be measured. This value is stored in Internal Temperature
Reading register (26h) and compared to the Temperature Limit registers (50h – 51h). If this value
violates the programmed limits in the Internal High Temperature Limit register (51h) or the Internal Low
Temperature Limit register (50h) the corresponding status bit in Interrupt Status Register 1 is set.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See the
section titled Auto Fan Control Operating Mode on page 30.
5.9.2 External Temperature Measurement
The Hardware Monitor Block also provides a way to measure two external temperatures using diode
sensor pins (Remote x+ and Remote x-). The value is stored in the register (25h) for Remote1+ and
Remote1- pins. The value is stored in the Remote Temperature Reading register (27h) for Remote2+
and Remote2- pins. If these values violate the programmed limits in the associated limit registers, then
the corresponding Remote Diode 1 (D1) or Remote Diode 2 (D2) status bits will be set in the Interrupt
Status Register 1.
If auto fan option is selected, the hardware will adjust the operation of the fans accordingly. See Auto
Fan Control Operating Mode on page 30.
Table 5.5 Min/Max ADC Conversion Table
INPUT VOLTAGE +12VIN +5VIN VCC/3.3VIN +2.5VIN +1.8VIN +1.5VIN +VCCP
Min Value (Corresponds
to A/D output 00000000)
<0.062 <0.026 <0.017 <0.013 <0.009 <0.008 <0.012
Max Value (Corresponds
to A/D output 11111111)
>15.938 >6.640 >4.383 >3.320 >2.391 >1.992 >2.988
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There are Remote Diode (1 or 2) Fault status bits in Interrupt Status Register 2 (42h), which, when
one, indicate a short or open-circuit on remote thermal diode inputs (Remote x+ and Remote x-).
Before a remote diode conversion is updated, the status of the remote diode is checked. In the case
of a short or open-circuit on the remote thermal diode inputs, the value in the corresponding reading
register will be forced to 80h. Note that this will cause the associated remote diode limit exceeded
status bit to be set (i.e. Remote Diode x Limit Error bits (D1 and D2) are located in the Interrupt Status
1 Register at register address 41h).
The temperature change is computed by measuring the change in Vbe at two different operating points
of the diode to which the Remote x+ and Remote x- pins are connected. But accuracy of the
measurement also depends on non-ideality factor of the process the diode is manufactured on.
5.9.3 Temperature Data Format
Temperature data can be read from the three temperature registers:
■Internal Temp Reading register (26h)
■Remote Diode 1 Temp Reading register (25h)
■Remote Diode 2 Temp Reading register (27h)
The following table shows several examples of the format of the temperature digital data, represented
by an 8-bit, two’s complement word with an LSB equal to 1.0 0C.
Table 5.6 Temperature Data Format
TEMPERATURE READING (DEC) READING (HEX) DIGITAL OUTPUT
-1270C -127 81h 1000 0001
…
…
…
…
-50 0C -50 CEh 1100 1110
…
…
…
…
-25 0C -25 E7h 1110 0111
…
…
…
…
-1 0C -1 FFh 1111 1111
0 0C 0 00h 0000 0000
+1 0C 1 01h 0000 0001
…
…
…
…
+25 0C 25 19h 0001 1001
…
…
…
…
+500C 50 32h 0011 0010
…
…
…
…
+1270C 127 7Fh 0111 1111
SENSOR ERROR 128 80h 1000 0000
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5.9.4 Offset Registers
There are three offset registers:
■Offset Register Ambient (1Dh)
■Offset Register 2 (1Eh)
■Offset Register 1 (1Fh)
Offset Register 1 is used for Remote Diode 1 Temp Reading. Offset Register 2 is used for Remote
Diode 2 Temp Reading. Offset Register Ambient is used for internal Temp Reading.
The Offset Registers contain a 2's complement value which is added (or subtracted if the number is
negative) to the corresponding temperature reading. The default value in the offset register is zero, so
initially zero is always added to the temperature reading.
5.10 Thermal Zones
Each temperature measurement input is assigned to a Thermal Zone to control the PWM outputs in
Auto Fan Control mode. These zone assignments are as follows:
■Zone 1 = Remote Diode 1 (Processor)
■Zone 2 = Ambient (Internal) Temperature Sensor
■Zone 3 = Remote Diode 2
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Chapter 6 Fan Control
The following sections describe the various fan control and monitoring modes in the part.
6.1 General Description
This Fan Control device is capable of driving multiple DC fans via three PWM outputs and monitoring
up to four fans equipped with tachometer outputs in either Manual Fan Control mode or in Auto Fan
Control mode. The three fan control outputs (PWMx pins) are controlled by a Pulse Width Modulation
(PWM) scheme. The four pins dedicated to monitoring the operation of each fan are the TACH[1:4]
pins. Fans equipped with Fan Tachometer outputs may be connected to these pins to monitor the
speed of the fan.
6.1.1 Limit and Configuration Registers
At power up, all the registers are reset to their default values and PWM[1:3] are set to “Fan always on
Full” mode. Before initiating the monitoring cycle for either manual or auto mode, the values in the limit
and configuration registers should be set.
The limit and configuration registers are:
■Registers 54h – 5Bh: TACHx Minimum
■Registers 5Fh – 61h: Zone x Range/FANx Frequency
■Registers 5Ch – 5Eh: PWMx Configuration
■Registers 62h − 63h: Min/Off, PWM x Ramp Rate Control
■Registers 64h – 66h: PWMx Minimum Duty Cycle
■Registers 67h – 69h: Zone x Low Temp LIMIT
■Registers 6Ah – 6Ch: Zone x Temp Absolute Limit – all fans in Auto Mode are set to full
■Registers 6Dh – 6Eh: Zone x Hysteresis
■Register 81h: TACH_PWM Association
■Registers 90h – 93h: Tachx Option Registers
■Registers 94h – 96h: PWMx Option Registers
The limit and configuration registers are defined in Chapter 7, Register Set.
Notes:
■The START bit in Register 40h Ready/Lock/Start Register must be set to ‘1’ to start temperature
monitoring functions.
■Setting the PWM Configuration register to Auto Mode will not take effect until after the START bit
is set
6.1.2 Device Set-Up
BIOS will follow the steps listed below to configure the fan registers on this device. The registers
corresponding to each function are listed. All steps may not be necessary if default values are
acceptable. Regardless of all changes made by the BIOS to the limit and parameter registers during
configuration, the EMC6D102 will continue to operate based on default values until the Start bit, in the
Ready/Lock/Start register, is set. Once the Start bit is set, the EMC6D102 will operate according to the
values that were set by BIOS in the limit and parameter registers.
1. Set limits and parameters (not necessarily in this order)
a. [5F-61h] Set PWM frequencies and Auto Fan Control Range.
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b. [62-63h] Set Ramp Rate Control and min/off
c. [5C-5Eh] Set the fan spin-up delays.
d. [5C-5Eh] Match each PWM output with a corresponding thermal zone.
e. [67-69h] Set the zone temperature low limits.
f. [6A-6Ch] Set the zone temperature absolute limits.
g. [64-66h] Set the PWM minimum duty cycle.
h. [6D-6Eh] Set the zone temperature Hysteresis values.
i. [81h] Associate a Tachometer input to a PWM output Register
j. [90-93h] Select the TACH Mode of operation (Mode 1 or Mode 2)
k. [90-93h] Programmed the PWM Max Stretch time (Mode 2 only)
l. [90-93h] Set the number of edges per tach reading
m. [90-93h] Set the ignore first 3 edges of tach input bit
n. [90-93h] Set the SLOW bit if tach reading should indicated slow fan or stalled fan event as FFFFh.
o. [94-96h] Set the TACH Reading Update rate
p. [94-96h] Set the tach reading guard time (Mode 2 Only)
q. [94-96h] Set the TACH reading logic for Opportunistic Mode (Mode 2 Only)
r. [94-96h] Set the SZEN bit, which determines if the PWM output will ramp to Off or jump to Off.
2. [40h] Set bit 0 (Start) to start monitoring.
3. [40h] Set bit 1 (Lock) to lock the limit and parameter registers (optional)
6.1.3 PWM Fan Speed Control
Note: The following description applies to PWM1, PWM2, and PWM3.
When describing the operation of the PWMs, the terms “Full on” and “100% duty cycle” means that
the PWM output will be high for 255 clocks and low for 1 clock (INVERT bit = 0). The exception to this
is during fan spin-up when the PWM pin will be forced high for the duration of the spin-up time.
6.1.3.1 Manual Fan Control Operating Mode (Test Mode)
When operating in Manual Fan Control Operating Mode, software controls the speed of the fans by
directly programming the PWM duty cycle. The operation of the fans can be monitored based on
reading the temperature and tachometer reading registers and/or by polling the interrupt status
registers. The EMC6D102 offers the option of generating an interrupt indicated by the INT# signal
located on the PWM2 and TACH3 pins.
To control the PWM outputs in manual mode:
■Write ‘111’ to bits[7:5] Zone/Mode, located in Registers 5Ch-5Eh: PWMx Configuration.
■The speed of the fan is controlled by the duty cycle set for that PWM output. The duty cycle must
be programmed in Registers 30h-32h: Current PWM Duty
To monitor the fans:
Fans equipped with Tachometer outputs can be monitored via the TACHx input pins. See Section 6.1.4,
"Fan Speed Monitoring," on page 37.
If an out-of-limit condition occurs, the corresponding status bit will be set in the Interrupt Status
registers. Setting this status bit will generate an interrupt signal on the INT# pin (if enabled). Software
must handle the interrupt condition and modify the operation of the device accordingly. Software can
evaluate the operation of the Fan Control device through the Temperature and Fan Tachometer
Reading registers.
When in manual mode, the current PWM duty cycle registers can be written to adjust the speed of the
fans, when the start bit is set. These registers are not writable when the lock bit is set.
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Note: The PWMx Current Duty Cycle register is implemented as two separate registers: a read-only
and a write-only. When a value is written to this register in manual mode there will be a delay
before the programmed value can be read back by software. The hardware updates the read-
only PWMx Current Duty Cycle register on the beginning of a PWM cycle. If Ramp Rate
Control is disabled, the delay to read back the programmed value will be from 0 seconds to
1/(PWM frequency) seconds. Typically, the delay will be 1/(2*PWM frequency) seconds.
6.1.3.2 Auto Fan Control Operating Mode
The EMC6D102 implements automatic fan control. In Auto Fan Mode, this device automatically adjusts
the PWM duty cycle of the PWM outputs, according to the flow chart on the following page (see
Figure 6.1 Automatic Fan Control Flow Diagramon page 31).
PWM outputs are assigned to a thermal zone based on the PWMx Configuration registers (see Section
5.10, "Thermal Zones," on page 27). It is possible to have more than one PWM output assigned to a
thermal zone. For example, PWM outputs 2 and 3, connected to two chassis fans, may both be
controlled by thermal zone 2. At any time, if the temperature of a zone exceeds its absolute limit, all
PWM outputs go to 100% duty cycle to provide maximum cooling to the system (except those fans
that are disabled or in manual mode).
It is possible to have a single fan controlled by multiple zones, turning on when either zone requires
cooling based on its individual settings.
A VCC POR resets all values to their initial or default states.
If the start bit is one, the Auto Fan Control block will evaluate the temperature in the zones configured
for each Fan in a round robin method. The Auto Fan Control block completely evaluates the zones for
all three fans in a maximum of 0.25sec.
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Figure 6.1 Automatic Fan Control Flow Diagram
*See Registers 5C-5Eh: PWM Configuration on page 59 for details.
When in Auto Fan Control Operating Mode the hardware controls the fans directly based on monitoring
of temperature and speed.
To control the fans:
1. Set the minimum temperature that will turn the fans on. This value is programmed in Registers 67h-
69h: Zone x Low Temp Limit (Auto Fan Mode Only).
2. Set the hysteresis value for the minimum temperature that will turn the fans off. This value will hold
the fans on until the temperature goes a certain amount below the value programmed in the Zone
x Low Temp Limit registers. This value will prevent the fan from oscillating between on and off if
the temperature is around the minimum temperature limit. This value is programmed in Registers
6Dh-6Eh: Zone Hysteresis registers.
Auto Fan Mode
Initiated
Temp >=
AbsLimit
(69~6B)
Override all PWM
outputs to 100%
duty cycle except
if disabled or in
manual mode
Temp >= Limit
(66~68)
No
Temp >=
Hyst Temp
(6C~6D)
No
Set Fan Output to
0%
No
Set fan output to
auto fan mode
minimum speed.
(63~65)
Yes
Fan Output
At 0%?
No
Yes
Fan Output
At 0%?
Yes
Set fan speed based on
Auto Fan Range
Algorithm*
No
Begin Fan Spin-
Up Yes
Set Fan Output to
100%
Fan Spinning
Up?
Spin Up
Time Elapsed?
(5C-5E)
Yes
Begin Polling
Cycle
End Polling
Cycle
No
No
End Fan Spin
Up
Yes
Off/Min set to 1?
(62) No
Yes
Set fan to min
PWM
Yes
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The speed of the fan is controlled by the duty cycle set for that device. The duty cycle for the minimum
fan speed must be programmed in Registers 64h-66h: PWMx Minimum Duty Cycle. This value
corresponds to the speed of the fan when the temperature reading is equal to the minimum
temperature LIMIT setting. As the actual temperature increases and is above the Zone LIMIT
temperature and below the Absolute Temperature Limit, the PWM will be determined by a linear
function based on the Auto Fan Speed Range bits in Registers 5Fh-61h.
Set the absolute temperature for each zone in Registers 6Ah-6Ch: Zone x Temp Absolute Limit (Auto
Fan Mode only). If the actual temperature is equal to or exceeds the absolute temperature in one or
more of the associated zones, all Fans operating in auto mode will be set to Full on, regardless of
which zone they are operating in (except those that are disabled or configured for Manual Mode).
Note: Fans can be disabled via the PWMx Configuration registers and the absolute temperature
safety feature can be disabled by writing 80h into the Zone x Temp Absolute Limit registers.
To set the mode to operate in auto mode, set Bits[7:5] Zone/Mode, located in Registers 5Ch-5Eh: PWM
Configuration Bits[7:5]=’000’ for PWM on Zone 1; Bits[7:5]=’001’ for PWM on Zone 2; Bits[7:5]=’010’
for PWM on Zone 3. If the “Hottest” option is chosen (101 or 110), then the PWM output is controlled
by the zone that results in the highest PWM duty cycle value.
Notes:
■Software can be alerted of an out-of-limit condition by the INT# pin if a status bit is set and enabled
and the interrupt function is enabled on either the PWM2 or TACH3 pins
■Software can monitor the operation of the Fans through the Fan Tachometer Reading registers and
by the PWM x Current PWM duty registers. It can also monitor current temperature readings
through the Temperature Limit Registers if hardware monitoring is enabled.
■Fan control in auto mode is implemented without any input from external processor .
In auto “Zone” mode, the speed is adjusted automatically as shown in the figure below. Fans are
assigned to a zone(s). It is possible to have more than one fan assigned to a thermal zone or to have
multiple zones assigned to one fan.
Figure 6.2 on page 33 shows the control for the auto fan algorithm. The part allows a minimum
temperature to be set, below which the fan will not run or will run at minimum speed (depending on
the setting of the Min/OFF bits). A hysteresis value is included to prevent the fan continuously
switching on and off if the temperature is close to the minimum. A temperature range is specified over
which the part will automatically adjust the fan speed. If the fan is off and the current temperature is
below the minimum temperature, then when the temperature exceeds the minimum, the fan will “spin
up” by going on full for a programmable amount of time. Following this spin up time, the fan will go to
a duty cycle computed by the auto fan algorithm. As the temperature rises, the duty cycle will increase
until the fan is running at full-speed when the temperature reaches the minimum plus the range value.
The effect of this is a temperature feedback loop, which will cause the temperature to reach equilibrium
between the minimum temperature and the minimum temperature plus the range. Provided that the
fan has adequate cooling capacity for all environmental and power dissipation conditions, this system
will maintain the temperature within acceptable limits, while allowing the fan to run slower (and quieter)
when less cooling is required.
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Figure 6.2 Automatic Fan Control
6.1.3.3 Spin Up
When a fan is being started from a stationary state (PWM duty cycle =00h), the part will cause the fan
to “spin up” by going to 100% duty cycle for a programmable amount of time to overcome the inertia
of the fan (i.e., to get the fan turning). Following this spin up time, the fan will go to the duty cycle
computed by the auto fan algorithm.
During spin-up, the PWM duty cycle is reported as 0%.
To limit the spin-up time and thereby reduce fan noise, the part uses feedback from the tachometers
to determine when each fan has started spinning properly. The following tachometer feedback is
included into the auto fan algorithm during spin-up.
Auto Fan operation during Spin Up:
The PWM goes to 100% duty cycle until the tachometer reading register is below the minimum limit
(see Figure 6.3), or the spin-up time expires, whichever comes first. This causes spin-up to continue
until the tachometer enters the valid count range, unless the spin up time expires. If the spin up expires
before the tachometer enters the valid range, an interrupt status bit will be set once spin-up expires.
Note that more than one tachometer may be associated with a PWM, in which case all tachometers
associated with a PWM must be in the valid range for spin-up to end.
Temp
Time
Tmax
=Tmin
+Trange
Tmin
PWM
Duty
Cycle
Time
Max
=FFh
min
Spin-Up
Time
Hysteresis
Hysteresis
Temperature
Temp
Time
Tmax
=Tmin
+Trange
Tmin
PWM
Duty
Cycle
Time
Max
=FFh
min
MIN/OFF bit = 0
(Fan off when temperature is below minimum)
MIN/OFF bit = 1
(Fan stays on when temperature is below minimum)
Notes:
1. When exiting spin-up, the PWM is set to the current calculated PWM
2. The PWM is set to OFF when the current temperature is less than
(Tmin-Hysteresis Temp)
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Figure 6.3 Spin Up Reduction Enabled
This feature defaults to enabled; it can be disabled by clearing bit 4 of the Configuration register (7Fh).
If disabled, the all fans go to 100% duty cycle for the duration of their associated spin up time. Note
that the Tachometer x minimum registers must be programmed to a value less than FFFFh in order
for the spin up reduction to work properly.
Notes:
■The tachometer reading register always gives the actual reading of the tachometer input.
■No interrupt bits are set during spin-up.
6.1.3.4 Hottest Option
If the “Hottest” option is chosen (101 or 110), then the fan is controlled by the limits and parameters
associated with the zone that requires the highest PWM duty cycle value, as calculated by the auto
fan algorithm.
6.1.3.5 Ramp Rate Control Logic
The Ramp Rate Control Logic, if enabled, limits the amount of change in the PWM duty cycle over a
specified period of time. This period of time is programmable in the Ramp Rate Control registers
located at offsets 62h and 63h.
RAMP RATE CONTROL DISABLED: (DEFAULT)
The Auto Fan Control logic determines the duty cycle for a particular temperature. If PWM Ramp Rate
Control is disabled, the PWM output will be set to this calculated duty cycle.
RAMP RATE CONTROL ENABLED:
If PWM Ramp Rate Control is enabled, the PWM duty cycle will Ramp up or down to the new duty
cycle computed by the auto fan control logic at the programmed Ramp Rate. The PWM Ramp Rate
Control logic compares the current duty cycle computed by the auto fan logic with the previous ramp
rate duty cycle. If the current duty cycle is greater than the previous ramp rate duty cycle the ramp
rate duty cycle is incremented by ‘1’ at the programmed ramp rate until it is greater than or equal to
the current calculated duty cycle. If the current duty cycle is less than the previous ramp rate duty
cycle, the ramp rate duty cycle is decremented by ‘1’ until it is less than or equal to the current duty
cycle. If the current PWM duty cycle is equal to the calculated duty cycle the PWM output will remain
unchanged.
Note: When Spin Up Reduction is enabled (SUREN), the Spin Up time will be less than
or equal to the programmed time for Spin Up. Once the tachometer(s) associated with a
PWM output are operating within the programmed limits or the Spin Up time expires,
whichever comes first, the PWM output is reduced to the calculated duty cycle.
PWM Output
Spin Up Time
tach reading
vs. tach limit FFFFh tach reading >
tach limit tach reading < tach limit
duty cycle = 100%
duty cycle = 0%
Programmed Spin Up Time
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Internally, the PWM Ramp Rate Control Logic will increment/decrement the internal PWM Duty cycle
by ‘1’ at a rate determined by the Ramp Rate Control Register (see Register 62h, 63h: Min/Off, PWM
Ramp Rate Control on page 62). The actual duty cycle output is changed once per the period of the
PWM output, which is determined by the frequency of the PWM output. (See Figure 6.4 Illustration of
PWM Ramp Rate Controlon page 36.)
■If the period of the PWM output is less than the step size created by the PWM Ramp Rate, the
PWM output will hold the duty cycle constant until the Ramp Rate logic increments/decrements the
duty cycle by ‘1’ again. For example, if the PWM frequency is 87.7Hz (1/87.7Hz = 11.4msec) and
the PWM Step time is 206msec, the PWM duty cycle will be held constant for a minimum of 18
periods (206/11.4 = 18.07) until the Ramp Logic increments/decrements the actual PWM duty cycle
by ‘1’.
■If the period of the PWM output is greater than the step size created by the PWM Ramp Rate, the
ramp rate logic will force the PWM output to increment/decrement the actual duty cycle in
increments larger than 1/255. For example, if the PWM frequency is 11Hz (1/11Hz = 90.9msec)
and the PWM Step time is 5msec, the PWM duty cycle output will be incremented 18 or 19 out of
255 (i.e., 90.9/5 = 18.18) until it reaches the calculated duty cycle.
Notes:
■The step size may be less if the calculated duty cycle minus the actual duty cycle is less than 18.
■The calculated PWM Duty cycle reacts immediately to a change in the temperature reading value.
The temperature reading value may be updated once in 624msec, once in 78msec, once in
223msec (default), or once in 447msec (see Table 5.2, “Conversion Cycle Timing,” on page 19).
The internal PWM duty cycle generated by the Ramp Rate control logic gradually ramps up/down
to the calculated duty cycle at a rate pre-determined by the value programmed in the PWM Ramp
Rate Control bits . The PWM output latches the internal duty cycle generated by the Ramp Rate
Control Block every 1/(PWM frequency) seconds to determine the actual duty cycle of the PWM
output pin.
PWM Output Transition from OFF to ON
When the calculated PWM Duty cycle generated by the auto fan control logic transitions from the ‘OFF’
state to the ‘ON’ state (i.e., Current PWM duty cycle>00h), the internal PWM duty cycle in the Ramp
Rate Control Logic is initialized to the calculated duty cycle without any ramp time and the PWMx
Current Duty Cycle register is set to this value. The PWM output will latch the current duty cycle value
in the Ramp Rate Control block to control the PWM output.
PWM Output Transition from ON to OFF
Each PWM output has a control bit to determine if the PWM output will transition immediately to the
OFF state (default) or if it will gradually step down to Off at the programmed Ramp Rate. These control
bits (SZEN) are located in the PWMx Options registers at offsets 94h-96h.
Table 6.1 PWM Ramp Rate
RRX-
[2:0]
PWM RAMP TIME (SEC)
(TIME FROM 33%
DUTY CYCLE TO
100% DUTY CYCLE)
PWM RAMP TIME (SEC)
(TIME FROM 0% DUTY
CYCLE TO 100% DUTY
CYCLE)
TIME PER
PWM STEP
(PWM STEP SIZE =
1/255)
PWM
RAMP
RATE
(HZ)
000 35 52.53 206 msec 4.85
001 17.6 26.52 104 msec 9.62
010 11.8 17.595 69 msec 14.49
011 7.0 10.455 41 msec 24.39
100 4.4 6.63 26 msec 38.46
101 3.0 4.59 18 msec 55.56
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Figure 6.4 Illustration of PWM Ramp Rate Control
Notes:
■The PWM Duty Cycle latches the Ramping Duty Cycle on the rising edge of the PWM output.
■The calculated duty cycle, ramping duty cycle, and the PWM output duty cycle are asynchronous
to each other, but are all synchronized to the internal 90kHz clock source.
It should be noted that the actual duty cycle on the pin is created by the PWM Ramp Rate Control
block and latched on the rising edge of the PWM output. Therefore, the current PWM duty cycle may
lag the PWM Calculated Duty Cycle.
110 1.6 2.55 10 msec 100
111 0.8 1.275 5 msec 200
Table 6.1 PWM Ramp Rate (continued)
RRX-
[2:0]
PWM RAMP TIME (SEC)
(TIME FROM 33%
DUTY CYCLE TO
100% DUTY CYCLE)
PWM RAMP TIME (SEC)
(TIME FROM 0% DUTY
CYCLE TO 100% DUTY
CYCLE)
TIME PER
PWM STEP
(PWM STEP SIZE =
1/255)
PWM
RAMP
RATE
(HZ)
Example 1: PWM period < Ramp Rate Step Size
PWM frequency = 87.7Hz (11.4msec) & PWM Ramp Rate = 38.46Hz (26msec)
Calculate Duty Cycle 70h 74h
PWM Duty Cycle 70h
11.4ms
11.4ms
11.4ms 11.4ms 11.4ms 11.4ms 11.4ms 11.4ms 11.4ms 11.4ms
71h 71h 71h 72h 72h 73h 73h 73h 74h 74h 74h
Example 2: PWM period > Ramp Rate Step Size
PWM frequency = 11Hz (90.9msec) & PWM Ramp Rate = 38.46Hz (26msec)
Calculate Duty Cycle 70h 74h
Ramping Duty Cycle
PWM Duty Cycle 70h
70h 71h 72h 73h 74h
26ms 26ms
26ms
26ms
Ramping Duty Cycle 70h 71h 72h 73h 74h
26ms 26ms
26ms26ms
90.9msec
71h 74h
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6.1.4 Fan Speed Monitoring
The chip monitors the speed of the fans by utilizing fan tachometer input signals from fans equipped
with tachometer outputs. The fan tachometer inputs are monitored by using the Fan Tachometer
registers. These signals, as well as the Fan Tachometer registers, are described below.
The tachometers will operate in one of two modes:
■Mode 1: Standard tachometer reading mode. This mode is used when the fan is always powered
when the duty cycle is greater than 00h.
■Mode 2: Enhanced tachometer reading mode. This mode is used when the PWM is pulsing the fan.
6.1.4.1 TACH Inputs
The tachometer inputs are implemented as digital input buffers with logic to filter out small glitches on
the tach signal.
6.1.4.2 Selecting the Mode of Operation:
The mode is selected through the Mode Select bits located in the Tach Option register. This Mode
Select bit is defined as follows:
■0=Mode 1: Standard tachometer reading mode
■1=Mode 2 (default): Enhanced tachometer reading mode.
Default Mode of Operation:
■Mode 2
■Max stretch time (800msec)
■Slow interrupt enabled (Force FFFEh)
■Tach interrupt enabled via enable bit
■Tach Limit = FFFFh
■Look for 5 tach edges
■Don’t ignore first 3 edges after guard time
■Guard Time = 32 clock periods (1 clock period = 1/90kHz).
■Tach readings updated once a second
6.1.4.3 Mode 1 – Always Monitoring
Mode 1 is the simple case. In this mode, the Fan is always powered when it is ‘ON’ and the fan
tachometer output ALWAYS has a valid output. This mode is typically used if a linear DC Voltage
control circuit drives the fan. In this mode, the fan tachometer simply counts the number of 90kHz
pulses between the programmed number of edges (default = 5 edges). The fan tachometer reading
registers are continuously updated.
Notes:
■Some enhanced features added to support Mode 2, are available to Mode 1 also. They are:
programmable number of tach edges and force tach reading register to FFFEh to indicate a SLOW
fan.
■Five edges or two tach pulses are generated per revolution.
The counter is used to determine the period of the Fan Tachometer input pulse. The counter starts
counting on the first edge and continues counting until it detects the last edge or until it reaches FFFFh.
If the programmed number of edges is detected on or before the counter reaches FFFFh, the reading
register is updated with that count value. If the counter reaches FFFFh and no edges were detected
a stalled fan event has occurred and the Tach Reading register will be set to FFFFh. If one or more
edges are detected, but less than the programmed number of edges, a slow fan event has occurred
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and the Tach Reading register will be set to either FFFEh or FFFFh depending on the state of the Slow
Tach bits located in the TACHx Options registers at offsets 90h - 93h. Software can easily compute
the RPM value using the tachometer reading value if it knows the number of edges per revolution.
6.1.4.4 Mode 2 –Monitor Tach input When PWM is ‘ON’
In this mode, the PWM is used to pulse the Fan motor of a 3-wire fan. 3-wire fans use the same
power supply to drive the fan motor and to drive the tachometer output logic. When the PWM is ‘ON’
the fan generates valid tach pulses. When the PWM is not driving the Fan, the tachometer signal is
not generated and the tach signal becomes indeterminate or tristate. Therefore, Mode 2 only makes
tachometer measurements when the associated PWM is driving high during an update cycle. As a
result, the Fan tachometer measurement is “synchronized” to the PWM output, such that it only looks
for tach pulses when the PWM is ‘ON’.
Note: Any fan tachometer input may be associated with any PWM output (see Linking Fan
Tachometers to PWMs on page 43.)
During an update cycle, if an insufficient number of tachometer pulses are detected during this time
period, the PWM output is “stretched” (held high) until either the programmed number of edges is
detected or the the maximum stretch time expires, whichever comes first. (See Summary of Operation
for Modes 1 & 2 on page 40)
PWM STRETCHING
PWM stretching will be done by the hardware each update of the tachometer registers (every 300ms,
500ms, or 1000ms). The PWM will be stretched until the programmed number of edges is detected or
until the programmed max PWM stretching timeout occurs. If at least one edge but less than the
programmed number of edges is detected, the fan is considered slow. If no edge is detected, the fan
is considered stopped.
Note: The interrupt status bits are set, if enabled, to indicate that a slow or stopped fan event has
occurred when the tach reading registers are greater than the tach limit registers.
The PWM maximum stretching times (50, 100, 200, 400, 600, 800, 950 msec) represent the maximum
time that the PWM will be ‘on’. So if the hardware needs to stretch the PWM ‘on’ time then it will be
stretched beyond the PWM duty cycle ‘on’ time up to the programmed PWM stretch time.
If PWM stretching is disabled, the tachometer will only be monitored during the PWM duty cycle ‘ON’
time. The hardware will never stretch the PWM ‘ON’ time. The hardware treats the disabled case as
Stretch Time equals PWM ‘ON’ time. Interrupts are reported in the same manner as if stretching is
enabled.
Note: When stretching is enabled, the hardware will continue the edge detection until the required
number of edges occur or the stretching time period expires.
ASSUMPTIONS (REFER TO FIGURE 4 - PWM AND TACHOMETER CONCEPT):
The Tachometer pulse generates 5 transitions per fan revolution (i.e., two fan tachometer periods per
revolution, edges 2→6). One half of a revolution (one tachometer period) is equivalent to three edges
(2→4 or 3→5). One quarter of a revolution (one-half tachometer period) is equivalent to two edges.
To obtain the fan speed, count the number of 90Khz pulses that occurs between 2 edges i.e., 2→3,
between 3 edges i.e., 2→4, or between 5 edges, i.e. 2→6 (the case of 9 edges is not shown). The
time from 1-2 occurs through the guard time and is not to be used. For the discussion below, an edge
is a high-to-low or low-to-high transition (edges are numbered – refer to Figure 4 - PWM and
Tachometer Concept
The Tachometer circuit begins monitoring the tach when the associated PWM output transitions high
and the guard time has expired. Each tach circuit will continue monitoring until either the stretch time
ends or the programmed number of edges has been detected, whichever comes first. The associated
PWM output will continue to stretch until all tachs that are associated with it have taken a
measurement.
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The Fan Tachometer value may be updated every 300ms, 500ms, or 1000ms.
Figure 6.5 PWM and Tachometer Concept
FAN TACHOMETER OPTIONS FOR MODE 2
■2, 3, 5 or 9 “edges” to calculate the fan speed (Figure 4)
■Guard time A is programmable (8-63 clocks) to account for delays in the system (Figure 4)
■PWM Stretching options: 50, 100, 200, 400, 600, 800msec, and 950msec.
■The PWM frequencies for modes 1 & 2 are: 11.0 Hz, 14.6 Hz, 21.9 Hz, 29.3 Hz, 35.2 Hz, 44.0 Hz,
58.6 Hz, 87.7Hz
■Option to ignore first 3 tachometer edges after guard time
■Option to force tach reading register to FFFEh to indicate a slow fan.
6.1.4.5 Fan Tachometer Reading Registers:
The Tachometer Reading registers are 16 bits, unsigned. When one byte of a 16-bit register is read, the
other byte latches the current value until it is read, in order to ensure a valid reading. The order is LSB first,
MSB second. The value FFFFh indicates that the fan is not spinning, or the tachometer input is not
connected to a valid signal (this could be triggered by a counter overflow). These registers are read
only – a write to these registers has no effect.
Notes:
■The Fan Tachometer Reading registers always return an accurate fan tachometer measurement,
even when a fan is disabled or non-functional.
■FFFFh indicates that the fan is not spinning, or the tachometer input is not connected to a valid
signal (This could be triggered by a counter overflow).
■The Tachometer registers are read only – a write to these registers has no effect.
■Mode 1 should be enabled and the tachometer limit register should be set to FFFFh if a tachometer
input is left unconnected.
Internal PWM
Signal
Window for
Valid Tach
Pulses
Guard time A
Tach
Pulses
Tach
Pulses
2345
16
BDF
ACE
PWM “ON”
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6.1.4.6 Programming Options for Each Tachometer Input
The features defined in this section are programmable via the TACHx Option registers located at
offsets 90h-93h and the PWMx Option registers located at offsets 94h-96h.
TACH READING UPDATE TIME
In Mode 1, the Fan Tachometer Reading registers are continuously updated. In Mode 2, the fan
tachometer registers are updated every 300ms, 500msec, or 1000msec. This option is programmed
via bits[1:0] in the PWMx Option register. The PWM associated with a particular TACH(s) determines
the TACH update time.
PROGRAMMED NUMBER OF TACH EDGES
In modes 1 & 2, the number of edges is programmable for 2, 3, 5 or 9 edges (i.e., ½ tachometer pulse,
1 tachometer pulse, 2 tachometer pulses, 4 tachometer pulses). This option is programmed via bits[2:1]
in the TachX Option register.
Note: The “5 edges” case corresponds to two tachometer pulses, or 1 RPM for most fans. Using
the other edge options will require software to scale the values in the reading register to
correspond to the count for 1 RPM.
GUARD TIME (MODE 2 ONLY)
The guard time is programmable from 8 to 63 clocks (90kHz). This option is programmed via bits[4:3]
in the TachX Option register.
PWM STRETCH TIME (MODE 2 ONLY)
The PWM max stretching time is programmable to 50msec, 100msec, 200msec, 400msec, 600msec,
800msec, and 950msec. This option is programmed via bits[7:5] in the TachX Option register. PWM
stretching can be disabled by selecting the bit combination 000 (default is disabled).
IGNORE FIRST 3 TACHOMETER EDGES (MODE 2 ONLY)
Option to ignore first 3 tachometer edges after guard time. This option is programmed for each
tachometer via bits[2:0] in the TACHx Option register. Default is do not ignore first 3 tachometer edges
after guard time.
6.1.4.7 Summary of Operation for Modes 1 & 2
The following summarizes the detection cases:
■No edge occurs during the PWM ‘ON’ time or stretching time: indicate this condition as a
stalled fan
−The tachometer reading register contains FFFFh.
■One edge (or less than programmed number of edges) occurs during the PWM ‘ON’ time or
stretching time: indicate this condition as a slow fan.
−If the SLOW bit is ‘0’, the tachometer reading register will be set to FFFEh to indicate that this is
a slow fan instead of a seized fan. Note: This operation also pertains to the case where the
tachometer counter reaches FFFFh before the programmed number of edges occurs.
−If the SLOW bit is ‘1’, the tachometer reading register will be set to FFFFh. In this case, no
distinction is made between a slow or seized fan.
Note: The Slow Interrupt Enable feature (SLOW) is configured in the TACHx Options registers at
offsets 90h to 93h.
■The programmed number of edges occurs:
-Mode 1: If the programmed number of edges occurs before the counter reaches FFFFh latch the
tachometer count
-Mode 2: If the programmed number of edges occurs during the PWM ‘ON’ time or stretching time:
latch the tachometer count and stop stretching PWM (see Note below).
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102 41 Revision 0.4 (04-05-05)
DATASHEET
Notes:
■Whenever the programmed number of edges is detected, the edge detection ends and the state
machine is reset. The tachometer reading register is updated with the tachometer count value at
this time. See Note 6.2 below Table 6.2 for the one exception to this behavior.
■In the case where the programmed number of edges occurs during the stretching time, the
tachometer value is latched when the last required edge is detected. The table below shows the
maximum values that may appear in the reading register.
Note 6.1 The maximum tachometer count does not take into account the guard time.
Note 6.2 This max value will be FFFFh if the programmed number of edges is detected when the
count reaches FFFFh or if no edges are detected. If the count reaches FFFFh in Mode 1
or the Max stretch time in Mode 2 and some edges were detected, but less than the
programmed number of edges, the maximum tach count value is determined by the Slow
Interrupt Enable bit located in the TACHx Options registers at offsets 90h to 93h. If slow
interrupt detection is enabled the count will be forced to FFFEh, else the count will be
forced to FFFFh.
6.1.4.8 Examples of Minimum RPMs Supported
The following tables show minimum RPMs that can be supported with the different parameters. The
first table uses 3 edges and the second table uses 2 edges.
Table 6.2 Max Tachometer Count Values for Different Stretch Periods
PWM STRETCHING PERIOD MAXIMUM TACHOMETER COUNT AT END OF PERIOD
(Note 6.1)
50ms 1194h
100ms 2328h
200ms 4650h
400ms 8CA0h
600ms D2F0h
800ms FFFFh (Note 6.2)
950ms FFFFh (Note 6.2)
Table 6.3 Minimum RPM Detectable Using 3 Edges – No PWM Stretching
PWM
FREQUENCY
PULSE WIDTH AT DUTY CYCLE
(PWM ”ON” TIME)
MINIMUM RPM AT DUTY CYCLE (Note 6.4)
(30/TTachPulse)
(HZ)
25%
(MSEC)
50%
(MSEC)
100%
(MSEC)
(Note 6.3) 25% 50% 100%
87.7 2.85 5.7 11.36 10865 5347 2662
58.6 4.27 8.53 17 7175 3554 1774
44 5.68 11.36 22.64 5366 2662 1330
35.2 7.1 14.2 28.3 4279 2126 1063
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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DATASHEET
Note 6.3 100% duty cycle is 255/256.
Note 6.4 RPM=60/TRevolution, TTachPulse= TRevolution/2. Using 3 edges for detection, TTachPulse =
(PWM ”ON” Time – Guard Time). Minimum RPM values shown use minimum guard time
(88.88usec).
Note 6.5 100% duty cycle is 255/256
Note 6.6 RPM=60/TRevolution, TTachPulse= TRevolution/2. Using 2 edges for detection, TTachPulse =
2*(PWM ”ON” Time-Guard Time). Minimum RPM values shown use minimum guard time
(88.88usec).
29.3 8.53 17.06 34 3554 1768 885
21.9 11.42 22.83 45.48 2648 1319 661
14.6 17.12 34.25 68.23 1761 878 440
11 22.73 45.45 90.55 1325 661 332
Table 6.4 Minimum RPM Detectable Using 2 Edges – No PWM Stretching
PWM
FREQUENCY
PULSE WIDTH AT DUTY CYCLE
(PWM ”ON” TIME)
MINIMUM RPM AT DUTY CYCLE (Note 6.6)
(30/TTachPulse)
(HZ)
25%
(MSEC)
50%
(MSEC)
100%
(MSEC)
(Note 6.5) 25% 50% 100%
87.7 2.85 5.7 11.36 5433 2673 1331
58.6 4.27 8.53 17 3588 1777 887
44 5.68 11.36 22.64 2683 1331 665
35.2 7.1 14.2 28.3 2139 1063 532
29.3 8.53 17.06 34 1777 884 442
21.9 11.42 22.83 45.48 1324 660 330
14.6 17.12 34.25 68.23 881 439 220
11 22.73 45.45 90.55 663 331 166
Table 6.3 Minimum RPM Detectable Using 3 Edges – No PWM Stretching (continued)
PWM
FREQUENCY
PULSE WIDTH AT DUTY CYCLE
(PWM ”ON” TIME)
MINIMUM RPM AT DUTY CYCLE (Note 6.4)
(30/TTachPulse)
(HZ)
25%
(MSEC)
50%
(MSEC)
100%
(MSEC)
(Note 6.3) 25% 50% 100%
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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SMSC EMC6D102 43 Revision 0.4 (04-05-05)
DATASHEET
Note: Minimum RPM values shown use minimum guard time (88.88usec).
6.1.4.9 Detection of a Stalled Fan
There is a fan failure bit (TACHx) in the interrupt status register used to indicate that a slow or stalled
fan event has occurred. If the tach reading value exceeds the value programmed in the tach limit
register the interrupt status bit is set. See Interrupt Status register 2 at offset 42h.
Notes:
■The reading register will be forced to FFFFh if a stalled event occurs (i.e., stalled event =no edges
detected.)
■The reading register will be forced to either FFFFh or FFFEh if a slow fan event occurs. (i.e., slow
event: 0 < #edges < programmed #edges). If the control bit, SLOW, located in the TACHx Options
registers at offsets 90h - 93h, is ‘0’ then FFFEh will be forced into the corresponding Tach Reading
Register to indicate that the fan is spinning slowly.
■The fan tachometer reading register stays at FFFFh in the event of a stalled fan. If the fan begins
to spin again, the tachometer logic will reset and latch the next valid reading into the tachometer
reading register.
6.1.4.10 Fan Interrupt Status Bits
The status bits for the fan events are in Interrupt Status Register 2 (42h). These bits are set when the
reading register is above the tachometer minimum and the Interrupt Enable 2 (Fan Tachs) register bits
are configured to enable Fan Tach events. No interrupt status bits are set for fan events (even if the
fan is stalled) if the associated tachometer minimum is set to FFFFh (registers 54h-5Bh).
Note: The Interrupt Enable 2 (Fan Tachs) register at offset 80h defaults to enabled for the individual
tachometer status events bits. The group Fan Tach INT# bit defaults to disabled. This bit needs
to be set if Fan Tach interrupts are to be generated on the external INT# pin.
See Figure 5.1 Interrupt Controlon page 22.
6.1.5 Linking Fan Tachometers to PWMs
The TACH/PWM Association Register at offset 81h is used to associate a Tachometer input with a
PWM output. This association has three purposes:
1. The auto fan control logic supports a feature called SpinUp Reduction. If SpinUp Reduction is
enabled (SUREN bit), the auto fan control logic will stop driving the PWM output high if the
associated TACH input is operating within normal parameters. (Note: SUREN bit is located in the
Configuration Register at offset 7Fh)
2. To measure the tachometer input in Mode 2, the tachometer logic must know when the associated
PWM is ‘ON’.
Table 6.5 Minimum RPM Detectable– With PWM Stretching
NUMBER OF EDGES
FOR DETECTION
MINIMUM RPM AT STRETCHED PULSE WIDTH
50MSEC 100MSEC 200MSEC 400MSEC 600MSEC 800MSEC 950MSEC
9 2400 1200 600 300 200 150 126
5 1200 600 300 150 100 75 63
3 600 300 150 75 50 38 32
2 300 150 75 38 25 19 16
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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DATASHEET
3. Inhibit fan tachometer interrupts when the associated PWM is ‘OFF’.
See the description of the PWM_TACH register. The default configuration is:
PWM1 -> TACH1.
PWM2 -> TACH2.
PWM3 -> TACH3 & TACH4.
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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SMSC EMC6D102 45 Revision 0.4 (04-05-05)
DATASHEET
Chapter 7 Register Set
Definition for the Lock and Start columns:
Yes = Register is made read-only when the related bit is set; No = Register is not made read-only
when the related bit is set.
Table 7.1 Register Summary
Reg
Addr
Read/
Write Reg Name Bit 7
MSb Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
LSb
Default
Value Lock Start
10h R/W SMSC Test Register 7654321000h No No
1Dh R/W Offset Register Ambient 7654321000h Yes No
1Eh R/W Offset Register 2 7654321000h Yes No
1Fh R/W Offset Register 1 7654321000h Yes No
20h R+2.5V Reading 76543210N/ANo No
21h RVccp Reading 76543210N/ANo No
22h RVCC Reading 76543210N/ANo No
23h R+5V Reading 76543210N/ANo No
24h R+12V Reading 76543210N/ANo No
25h RRemote Diode 1 Temp Reading 76543210N/ANo No
26h RInternal Temp Reading 76543210N/ANo No
27h RRemote Diode 2 Temp Reading 76543210N/ANo No
28h RTach1 LSB 76543210N/ANo No
29h RTach1 MSB 15 14 13 12 11 10 9 8 N/A No No
2Ah RTach2 LSB 76543210N/ANo No
2Bh RTach2 MSB 15 14 13 12 11 10 9 8 N/A No No
2Ch RTach3 LSB 76543210N/ANo No
2Dh RTach3 MSB 15 14 13 12 11 10 9 8 N/A No No
2Eh RTach4 LSB 76543210N/ANo No
2Fh RTach4 MSB 15 14 13 12 11 10 9 8 N/A No No
30h R/W
Note 7.1
PWM1 Current Duty Cycle 76543210N/AYes
Note 7.1
No
31h R/W
Note 7.1
PWM2 Current Duty Cycle 76543210N/AYes
Note 7.1
No
32h R/W
Note 7.1
PWM3 Current Duty Cycle 76543210N/AYes
Note 7.1
No
3Eh RCompany ID 765432105Ch No No
3Fh RVersion / Stepping VER3 VER2 VER1 VER0 STP3 STP2 STP1 STP0 65h No No
40h R/W
Note 7.2
Ready/Lock/Start RES RES RES RES OVRID READY LOCK START 00h Yes
Note 7.2
No
41h R-C
Note 7.3
Interrupt Status Register 1 INT2 D2 AMB D1 5V VCC Vccp 2.5V 00h No No
42h R-C
Note 7.3
Interrupt Status Register 2 ERR2 ERR1 TACH4 TACH3 TACH2 TACH1 RES 12V 00h No No
43h RVID0-4 RES RES RES VID4 VID3 VID2 VID1 VID0 N/A No No
44h R/W 2.5V Low Limit 7654321000h No No
45h R/W 2.5V High Limit 76543210FFh No No
46h R/W Vccp Low Limit 7654321000h No No
47h R/W Vccp High Limit 76543210FFh No No
48h R/W VCC Low Limit 7654321000h No No
49h R/W VCC High Limit 76543210FFh No No
4Ah R/W 5V Low Limit 7654321000h No No
4Bh R/W 5V High Limit 76543210FFh No No
4Ch R/W 12V Low Limit 7654321000h No No
4Dh R/W 12V High Limit 76543210FFh No No
4Eh R/W Remote Diode 1 Low Temp 7654321081h No No
4Fh R/W Remote Diode 1 High Temp 765432107Fh No No
50h R/W Internal Low Temp 7654321081h No No
51h R/W Internal High Temp 765432107Fh No No
52h R/W Remote Diode 2 Low Temp 7654321081h No No
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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53h R/W Remote Diode 2 High Temp 765432107Fh No No
54h R/W Tach1 Minimum LSB 76543210FFh No No
55h R/W Tach1 Minimum MSB 15 14 13 12 11 10 9 8 FFh No No
56h R/W Tach2 Minimum LSB 76543210FFh No No
57h R/W Tach2 Minimum MSB 15 14 13 12 11 10 9 8 FFh No No
58h R/W Tach3 Minimum LSB 76543210FFh No No
59h R/W Tach3 Minimum MSB 15 14 13 12 11 10 9 8 FFh No No
5Ah R/W Tach4 Minimum LSB 76543210FFh No No
5Bh R/W Tach4 Minimum MSB 15 14 13 12 11 10 9 8 FFh No No
5Ch R/W PWM 1 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h Yes No
5Dh R/W PWM 2 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h Yes No
5Eh R/W PWM 3 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h Yes No
5Fh R/W Zone 1 Range/PWM 1 Fre-
quency
RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h Yes No
60h R/W Zone 2 Range/PWM 2 Fre-
quency
RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h Yes No
61h R/W Zone 3 Range/PWM 3 Fre-
quency
RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h Yes No
62h R/W Min/Off, PWM1 Ramp Rate Con-
trol
OFF3 OFF2 OFF1 RES RR1E RR1-2 RR1-1 RR1-0 00h Yes No
63h R/W PWM 2, PWM3 Ramp Rate Con-
trol
RR2E RR2-2 RR2-1 RR2-0 RR3E RR3-2 RR3-1 RR3-0 00h Yes No
64h R/W PWM 1 MINIMUM Duty Cycle 7654321080h Yes No
65h R/W PWM 2 MINIMUM Duty Cycle 7654321080h Yes No
66h R/W PWM 3 MINIMUM Duty Cycle 7654321080h Yes No
67h R/W Zone 1 Low Temp Limit 765432105Ah Yes No
68h R/W Zone 2 Low Temp Limit 765432105Ah Yes No
69h R/W Zone 3 Low Temp Limit 765432105Ah Yes No
6Ah R/W Zone 1 Temp Absolute Limit 7654321064h Yes No
6Bh R/W Zone 2 Temp Absolute Limit 7654321064h Yes No
6Ch R/W Zone 3 Temp Absolute Limit 7654321064h Yes No
6Dh R/W Zone 1, Zone 2 Hysteresis H1-3 H1-2 H1-1 H1-0 H2-3 H2-2 H2-1 H2-0 44h Yes No
6Eh R/W Zone 3, Hysteresis H3-3 H3-2 H3-1 H3-0 RES RES RES RES 40h Yes No
6Fh R/W XOR Test Tree Enable RES RES RES RES RES RES RES XEN 00h Yes No
70h RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A No No
71h RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A No No
72h RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A No No
73h RSMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h No No
74h R/W SMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h Yes No
75h RSMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h No No
76h R/W SMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h Yes No
77h RSMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h No No
78h R/W SMSC Test Register RES RES RES RES TST3 TST2 TST1 TST0 09h Yes No
79h R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h Yes No
7Ah RSMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h No No
7Bh R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h Yes No
7Ch R/W
Note 7.4
Special Function Register AVG2 AVG1 AVG0 SMSC
Note 7.7
SMSC
Note 7.7
INTEN MON-
MD
LPMD
Note 7.5
40h Yes
Note 7.4
No
7Dh RReserved RES RES RES RES RES RES RES RES 00h No No
7Eh R/W Interrupt Enable 1 (Voltages) VCC 12V 5V RES VCCP 25V RES VOLT ECh Yes No
7Fh R/W Configuration INIT SMSC
Note 7.7
SMSC
Note 7.7
SUREN TRDY RES P2INT T3INT 10h Yes No
80h R/W Interrupt Enable 2 (Fan Tachs) RES RES RES TACH4 TACH3 TACH2 TACH1 TACH 1Eh Yes No
81h R/W TACH_PWM Association T4H T4L T3H T3L T2H T2L T1H T1L A4h Yes No
82h R/W Interrupt Enable 3 (Temp) RES RES RES RES D2EN D1EN AMB TEMP 0Eh Yes No
83h RReserved RES RES RES RES RES RES RES RES 00h No No
84h RReserved RES RES RES RES RES RES RES RES 00h No No
85h RA/D Converter LSbs Reg 1 RD2.3 RD2.2 RD2.1 RD2.0 RD1.3 RD1.2 RD1.1 RD1.0 N/A No No
86h RA/D Converter LSbs Reg 2 V12.3 V12.2 V12.1 V12.0 AM.3 AM.2 AM.1 AM.0 N/A No No
Table 7.1 Register Summary (continued)
Reg
Addr
Read/
Write Reg Name Bit 7
MSb Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
LSb
Default
Value Lock Start
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102 47 Revision 0.4 (04-05-05)
DATASHEET
Note: SMSC Test Registers may be read/write registers. Writing these registers can cause unwanted
results.
Note 7.1 The PWMx Current Duty Cycle Registers are only writable when the associated fan is in
manual mode. In this case, the register is writable when the start bit is set, but not when
the lock bit is set.
Note 7.2 The Lock and Start bits in the Ready/Lock/Start register are locked by the Lock Bit. The
OVRID bit is always writable, both when the start bit is set and when the lock bit is set.
Note 7.3 The Interrupt status registers are cleared on a read if no events are active
Note 7.4 The INTEN bit in register 7Ch is always writable, both when the start bit is set and when
the lock bit is set.
Note 7.5 In Shutdown Mode (LPMD=1 & START=0) all the H/W Monitoring registers/bits are not
accessible except for the following: Bits[2:0] in the Special Function Register (SFTR) at
offset 7Ch and Bits[7:0] in the Configuration register at offset 7Fh.
Note 7.6 These Reserved bits are read/write bits. Writing these bits to a ‘1’ has no effect on the
hardware.
Note 7.7 SMSC bits may be read/write bits. Writing these bits to a value other than the default value
may cause unwanted results
7.1 Undefined Registers
The registers shown in the table above are the defined registers in the part. Any reads to undefined
registers always return 00h. Writes to undefined registers have no effect and do not return an error.
87h RA/D Converter LSbs Reg 3 V50.3 V50.2 V50.1 V50.0 V25.3 V25.2 V25.1 V25.0 N/A No No
88h RA/D Converter LSbs Reg 4 VCC.3 VCC.2 VCC.1 VCC.0 VCP.3 VCP.2 VCP.1 VCP.0 N/A No No
89h RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A No No
8Ah RSMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 4Dh No No
8Bh R/W SMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 4Dh Yes No
8Ch RSMSC Test Register RES RES RES TST4 TST3 TST2 TST1 TST0 09h No No
8Dh R/W SMSC Test Register RES RES RES TST4 TST3 TST2 TST1 TST0 09h Yes No
8Eh RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A No No
8Fh RReserved RES RES RES RES RES RES RES RES 00h No No
90h R/W Tach1 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh No No
91h R/W Tach2 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh No No
92h R/W Tach3 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh No No
93h R/W Tach4 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh No No
94h R/W PWM1 Option RES
Note 7.6
RES
Note 7.6
OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch Yes No
95h R/W PWM2 Option RES
Note 7.6
RES
Note 7.6
OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch Yes No
96h R/W PWM3 Option RES
Note 7.6
RES
Note 7.6
OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch Yes No
97h R/W SMSC Test Register TST7 TST 6 TST 5 TST 4 TST3 TST2 TST1 TST0 5Ah Yes No
98h R/W SMSC Test Register TST7 TST 6 TST 5 TST 4 TST3 TST2 TST1 TST0 F1h Yes No
99-FEh R Reserved RES RES RES RES RES RES RES RES 00h No No
FFh R SMSC Test Register TST7 TST 6 TST 5 TST 4 TST3 TST2 TST1 TST0 N/A No No
Table 7.1 Register Summary (continued)
Reg
Addr
Read/
Write Reg Name Bit 7
MSb Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
LSb
Default
Value Lock Start
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
Revision 0.4 (04-05-05) 48 SMSC EMC6D102
DATASHEET
7.2 Defined Registers
7.2.1 Register 10h: SMSC Test Register
Setting the Lock bit has no effect on this register.
This register must not be written. Writing this register may produce unexpected results.
7.2.2 Register 1Dh, 1Eh, 1Fh: Offset Registers
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Offset Register Ambient only applies to the internal (ambient) temperature reading. This register
contains a 2's complement value, which is added (or subtracted if the number is negative) to the
ambient temperature reading. The default value in the offset register is zero, so initially zero is always
added to the temperature reading.
Offset Register 2 only applies to the remote diode 2 temperature reading. This register contains a
2's complement value, which is added (or subtracted if the number is negative) to external temperature
reading 2. The default value in the offset register is zero, so initially zero is always added to the
temperature reading.
Offset Register 1 only applies to the remote diode 1 temperature reading. This register contains a
2's complement value, which is added (or subtracted if the number is negative) to the external
temperature reading 1 reading. The default value in the offset register is zero, so initially zero is always
added to the temperature reading.
7.2.3 Registers 20-24h: Voltage Reading
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
10h R/W SMSC TEST TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
1Dh R/W Offset Register Ambient 7 6 5 4 3 2 1 0 00h
1Eh R/W Offset Register 2 7 6 5 4 3 2 1 0 00h
1Fh R/W Offset Register 1 7 6 5 4 3 2 1 0 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
20h R+2.5V Reading 7 6 5 4 3 2 1 0 N/A
21h RVccp Reading 7 6 5 4 3 2 1 0 N/A
22h RVCC Reading 7 6 5 4 3 2 1 0 N/A
23h R+5V Reading 7 6 5 4 3 2 1 0 N/A
24h R+12V Reading 7 6 5 4 3 2 1 0 N/A
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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DATASHEET
The Voltage Reading registers reflect the current voltage of the EMC6D102 voltage monitoring inputs.
Voltages are presented in the registers at ¾ full scale for the nominal voltage, meaning that at nominal
voltage, each register will read C0h.
The Voltage Reading registers will be updated automatically by the EMC6D102 Chip with a minimum
frequency of 4Hz. These registers are read only – a write to these registers has no effect.
7.2.4 Registers 25-27h: Temperature Reading
The Temperature Reading registers reflect the current temperatures of the internal and remote diodes.
Remote Diode 1 Temp Reading register reports the temperature measured by the Remote1- and
Remote1+ pins, Remote Diode 2 Temp Reading register reports the temperature measured by the
Remote2- and Remote2+ pins, and the Internal Temp Reading register reports the temperature
measured by the internal (ambient) temperature sensor. Current temperatures are represented as 8
bit, 2’s complement, signed numbers in Celsius, as shown below in Ta b le 7.3. The Temperature
Reading register will return a value of 80h if the remote diode pins are not implemented by the board
designer or are not functioning properly (this corresponds to the diode fault interrupt status bits). The
Temperature Reading registers will be updated automatically by the EMC6D102 Chip with a minimum
frequency of 4Hz.
Note: These registers are read only – a write to these registers has no effect.
Each of the temperature reading registers are mapped to a zone. Each PWM may be programmed to
operate in the auto fan control operating mode by associating a PWM with one or more zones. The
following is a list of the zone associations.
■Zone 1 is controlled by Remote Diode 1 Temp Reading
■Zone 2 is controlled by Internal Temp Reading (Ambient Temperature Sensor)
■Zone 3 is controlled by Remote Diode 2 Temp Reading
Table 7.2 Voltage vs. Register Reading
INPUT
NOMINAL
VOLTAGE
REGISTER
READING AT
NOMINAL
VOLTAGE
MAXIMUM
VOLTAGE
REGISTER
READING AT
MAXIMUM
VOLTAGE
MINIMUM
VOLTAGE
REGISTER
READING AT
MINIMUM VOLTAGE
+2.5V 2.5V C0h 3.32V FFh 0V 00h
Vccp 2.25V C0h 3.00V FFh 0V 00h
VCC 3.3V C0h 4.38V FFh 0V 00h
+5V 5.0V C0h 6.64V FFh 0V 00h
+12V 12.0V C0h 16.00V FFh 0V 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
25h RRemote Diode 1 Temp Reading 7 6 5 4 3 2 1 0 N/A
26h RInternal Temp Reading 7 6 5 4 3 2 1 0 N/A
27h RRemote Diode 2 Temp Reading 7 6 5 4 3 2 1 0 N/A
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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7.2.5 Registers 28-2Fh: Fan Tachometer Reading
The Fan Tachometer Reading registers contain the number of 11.111µs periods (90KHz) between full
fan revolutions. Fans produce two tachometer pulses per full revolution. These registers are updated
at least once every second.
This value is represented for each fan in a 16 bit, unsigned number.
The Fan Tachometer Reading registers always return an accurate fan tachometer measurement, even
when a fan is disabled or non-functional, including when the start bit=0.
When one byte of a 16-bit register is read, the other byte latches the current value until it is read, in
order to ensure a valid reading. The order is LSB first, MSB second.
FFFFh indicates that the fan is not spinning, or the tachometer input is not connected to a valid signal
(This could be triggered by a counter overflow).
These registers are read only – a write to these registers has no effect.
Table 7.3 Temperature vs. Register Reading
TEMPERATURE READING (DEC) READING (HEX)
-127°c-127 81h
.
.
.
.
.
.
.
.
.
-50°c-50 CEh
.
.
.
.
.
.
.
.
.
0°c 0 00h
.
.
.
.
.
.
.
.
.
50°c50 32h
.
.
.
.
.
.
.
.
.
127°c127 7Fh
(SENSOR ERROR) 80h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
28h R Tach1 LSB 7 6 5 4 3 2 1 0 N/A
29h R Tach1 MSB 15 14 13 12 11 10 9 8 N/A
2Ah R Tach2 LSB 7 6 5 4 3 2 1 0 N/A
2Bh R Tach2 MSB 15 14 13 12 11 10 9 8 N/A
2Ch R Tach3 LSB 7 6 5 4 3 2 1 0 N/A
2Dh R Tach3 MSB 15 14 13 12 11 10 9 8 N/A
2Eh R Tach4 LSB 7 6 5 4 3 2 1 0 N/A
2Fh R Tach4 MSB 15 14 13 12 11 10 9 8 N/A
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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7.2.6 Registers 30-32h: Current PWM Duty
Note 7.8 These registers are only writable when the associated fan is in manual mode. These
registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
The Current PWM Duty registers store the duty cycle that the chip is currently driving the PWM signals
at. At initial power-on, the duty cycle is 100% and thus, when read, this register will return FFh. After
the Ready/Lock/Start Register Start bit is set, this register and the PWM signals are updated based
on the algorithm described in the Auto Fan Control Operating Mode section and the Ramp Rate
Control logic, unless the associated fan is in manual mode – see below.
Note: When the device is configured for Manual Mode, the Ramp Rate Control logic should be
disabled.
When read, the Current PWM Duty registers return the current PWM duty cycle for the respective
PWM signal.
These registers are read only – a write to these registers has no effect.
Note: If the current PWM duty cycle registers are written while the part is not in manual mode or
when the start bit is zero, the data will be stored in internal registers that will only be active
and observable when the start bit is set and the fan is configured for manual mode. While the
part is not in manual mode and the start bit is zero, the current PWM duty cycle registers will
read back FFh.
Manual Mode (Test Mode)
In manual mode, when the start bit is set to 1 and the lock bit is 0, the current duty cycle registers are
writeable to control the PWMs.
Note: When the lock bit is set to 1, the current duty cycle registers are Read-Only.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
30h R/W
(See
Note 7.8)
PWM1 Current Duty Cycle 7 6 5 4 3 2 1 0 N/A
31h R/W
(See
Note 7.8)
PWM2 Current Duty Cycle 7 6 5 4 3 2 1 0 N/A
32h R/W
(See
Note 7.8)
PWM3 Current Duty Cycle 7 6 5 4 3 2 1 0 N/A
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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The PWM duty cycle is represented as follows:
During spin-up, the PWM duty cycle is reported as 0%.
Notes:
■The PWMx Current Duty Cycle always reflects the current duty cycle on the associated PWM pin.
■The PWMx Current Duty Cycle register is implemented as two separate registers: a read-only and
a write-only. When a value is written to this register in manual mode there will be a delay before
the programmed value can be read back by software. The hardware updates the read-only PWMx
Current Duty Cycle register on the beginning of a PWM cycle. If Ramp Rate Control is disabled,
the delay to read back the programmed value will be from 0 seconds to 1/(PWM frequency)
seconds. Typically, the delay will be 1/(2*PWM frequency) seconds.
7.2.7 Register 3Eh: Company ID
The Company ID register contains the company identification number. This number is a method for
uniquely identifying the part manufacturer.
This register is read only – a write to this register has no effect.
7.2.8 Register 3Fh: Version / Stepping
The four least significant bits of the Version / Stepping register [3:0] contain the current stepping of the
EMC6D102 silicon. The four most significant bits [7:4] reflect the version number.
The register is used by application software to identify which device has been implemented in the given
system. Based on this information, software can determine which registers to read from and write to.
Further, application software may use the current stepping to implement work-arounds for bugs found
in a specific silicon stepping. This register is read only – a write to this register has no effect.
Table 7.4 PWM Duty vs Register Reading
CURRENT DUTY VALUE (DECIMAL) VALUE (HEX)
0% 0 00h
…
…
…
25% 64 40h
…
…
…
50% 128 80h
…
…
…
100% 255 FFh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
3Eh RCompany ID 7 6 5 4 3 2 1 0 5Ch
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
3Fh RVersion / Stepping VER3 VER
2
VER
1
VER
0
STP
3
STP
2
STP
1
STP0 65h
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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7.2.9 Register 40h: Ready/Lock/Start Monitoring
Setting the Lock bit makes the Lock and Start bits read-only.
Note: There is a start-up time of up to 82ms for monitoring after the start bit is set to ‘1’, during which
time the reading registers are not valid.
The following summarizes the operation of the part based on the Start bit:
1. If Start bit = '0' then:
a. Fans are set to Full On.
b. No voltage, temperature, or fan tach monitoring is performed. The values in the reading registers
will be N/A (Not Applicable), which means these values will not be considered valid readings until
the Start bit = '1'. The exception to this is the Tachometer reading registers, which always give the
actual reading on the TACH pins.
c. No Status bits are set.
2. If Start bit = '1'
a. All fan control and monitoring will be based on the current values in the registers. There is no need
to preserve the default values after software has programmed these registers because no
monitoring or auto fan control will be done when Start bit = '0'.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
40h R/W Ready/Lock/Start RES RES RES RES OVRID READY LOCK START 00h
BIT NAME R/W DEFAULT DESCRIPTION
0START R/W 0 When software writes a 1 to this bit, the EMC6D102 enables
monitoring and PWM output control functions based on the limit and
parameter registers. Before this bit is set, the part does not update
register values. Whenever this bit is set to 0, the monitoring and PWM
output control functions are based on the default limits and parameters,
regardless of the current values in the limit and parameter registers.
The EMC6D102 preserves the values currently stored in the limit and
parameter registers when this bit is set or cleared. This bit becomes
read only when the Lock bit is set.
Note: When this bit is 0, all fans are on full 100% duty cycle, i.e.,
PWM pins are high for 255 clocks, low for 1 clock. When this
bit is 0, the part is not monitoring.
It is expected that all limit and parameter registers will be set by BIOS
or application software prior to setting this bit because these registers
cannot be written once the start bit is set.
1LOCK R/W 0 Setting this bit to 1 locks specified limit and parameter registers. Once
this bit is set, limit and parameter registers become read only and will
remain locked until the device is powered off. This register bit becomes
read only once it is set.
2READY R 0 The EMC6D102 sets this bit automatically after the part is fully
powered up, has completed the power-up-reset process, and after all
A/D converters are functioning (all bias conditions for the A/Ds have
stabilized and the A/Ds are in operational mode). (Always reads back
‘1’.)
3OVRID R/W 0 If this bit is set to 1, all PWM outputs go to 100% duty cycle regardless
of whether or not the lock bit is set.
4-7 Reserved R 0 Reserved.
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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b. Status bits may be set.
c. Setting the START bit to 1 does not prevent the limit and parameter registers from being written.
Note: Once programmed, the register values will be saved when start bit is reset to ‘0’.
7.2.10 Register 41h: Interrupt Status Register 1
Note 7.9 This register is cleared on a read if no events are active.
Note: The individual enable bits for D2, AMB, and D1 are located in the Interrupt Enable 3 (Temp)
register at offset 82h. The individual enable bits for 5V, VCC, Vccp, and 2.5V are located in
the Interrupt Enable 1 register at offset 7Eh.
The Interrupt Status Register 1 bits are automatically set by the device, if enabled, whenever the 2.5V,
Vccp, 3.3V, or 5V input voltages violate the limits set in the limit and parameter registers or when the
measured temperature violates the limits set in the limit and parameter registers for any of the three
thermal inputs.
This register holds a bit set until the event is read by software or until the individual enable bit is
cleared (see Note below). The contents of this register are cleared (set to 0) automatically by the
EMC6D102 after it is read by software, if the voltage or temperature no longer violates the limits set
in the limit and parameter registers. Once set, the Interrupt Status Register 1 bits remain set until a
read event occurs or until the individual enable bits is cleared, even if the voltage or temperature no
longer violate the limits set in the limit and parameter registers. Note that clearing the group Temp,
Fan, or Volt enable bits or the global INTEN enable bit has no effect on the status bits. See Registers
44-4Dh: Voltage Limit Registers on page 57 and on page 57.
This register contains a bit that indicates that a bit is set in the other interrupt status register. If bit 7
is set, then a status bit is set in the Interrupt Status Register 2. Therefore, S/W can poll this register,
and only if bit 7 is set does the other register need to be read. This bit is cleared (set to 0) automatically
by the device if there are no bits set in Interrupt Status Registers 2.
This register is read only – a write to this register has no effect.
Note: Clearing the individual enable bits:
1. An interrupt status bit will never change from a 0 to a 1 when the corresponding individual interrupt
enable bit is cleared (set to 0), regardless of whether the limits are violated during a measurement.
2. If the individual enable bit is cleared while the associated status bit is 1, the status bit will be
cleared when the associated reading register is updated. The reading registers only get updated
when the START bit is set to ‘1’. If the enable bit is cleared when the START bit is 0, the associated
interrupt status bit will not be cleared until the start bit is set to 1 and the associated reading register
is updated.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
41h R-C
(See
Note 7.9)
Interrupt Status 1 INT2 D2 AMB D1 5V VCC Vccp 2.5V 00h
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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7.2.11 Register 42h: Interrupt Status Register 2
Note 7.10 This register is cleared on a read if no events are active.
This register is read only – a write to this register has no effect.
The Interrupt Status Register 2 bits is automatically set by the device whenever a remote temperature
sensor error occurs, a tach reading value is above the minimum value set in the tachometer minimum
registers, or whenever the 12V input voltage violates the limits set in the limit and parameter registers.
The Interrupt Status Register 2 register holds a set bit until the event is read by software or until the
individual interrupt enable bit is cleared.
This register holds a bit set until the event is read by software or until the individual enable bit is
cleared (see Note below). The contents of this register are cleared (set to 0) automatically by the
EMC6D102 after it is read by software, if the voltage no longer violate the limits set in the limit and
parameter registers, if the temperature sensor error no loner exists, or if the tach reading register is
no longer above the minimum. Once set, the Interrupt Status Register 2 bits remain set until a read
event occurs or until the individual interrupt enable bit is cleared, even if the voltage, Tach, or diode
event no longer exists.
The remote diode fault bits do not clear on a read while the fault condition exists. If the start bit is set
when a fault condition occurs, 80h will be loaded into the associated temperature reading register,
which will cause the associated diode limit error bit to be set (Remote Diode 1 Limit Error or Remote
BIT NAME R/W DEFAULT DESCRIPTION
02.5V_Error R 0 The EMC6D102 automatically sets this bit to 1 when the 2.5V input
voltage is less than or equal to the limit set in the 2.5V Low Limit register
or greater than the limit set in the 2.5V High Limit register.
1Vccp_Error R 0 The EMC6D102 automatically sets this bit to 1 when the Vccp input
voltage is less than or equal to the limit set in the Vccp Low Limit register
or greater than the limit set in the Vccp High Limit register.
2VCC_Error R 0 The EMC6D102 automatically sets this bit to 1 when the VCC input
voltage is less than or equal to the limit set in the VCC Low Limit register
or greater than the limit set in the VCC High Limit register.
35V_Error R 0 The EMC6D102 automatically sets this bit to 1 when the 5V input voltage
is less than or equal to the limit set in the 5V Low Limit register or greater
than the limit set in the 5V High Limit register.
4Remote
Diode 1 Limit
Error
R 0 The EMC6D102 automatically sets this bit to 1 when the temperature
input measured by the Remote1- and Remote1+ is less than or equal to
the limit set in the Remote Diode 1 Low Temp register or greater than the
limit set in Remote Diode 1 High Temp register.
5Internal
Sensor Limit
Error
R 0 The EMC6D102 automatically sets this bit to 1 when the temperature
input measured by the internal temperature sensor is less than or equal
to the limit set in the Internal Low Temp register or greater than the limit
set in the Internal High Temp register.
6Remote
Diode 2 Limit
Error
R 0 The EMC6D102 automatically sets this bit to 1 when the temperature
input measured by the Remote2- and Remote2+ is less than or equal to
the limit set in the Remote Diode 2 Low Temp register or greater than the
limit set in the Remote Diode 1 High Temp register.
7INT2 Event
Active
R 0 The device automatically sets this bit to 1 when a status bit is set in the
Interrupt Status Register 2.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
42h R-C
(See
Note
7.10)
Interrupt Status Register 2 ERR2 ERR1 TACH4 TACH3 TACH2 TACH1 RES 12V 00h
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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Diode 2 Limit Error) in addition to the diode fault bit. Disabling the enable bit for the diode will clear
both the fault bit and the error bit for that diode (see Note below).
This register is read only – a write to this register has no effect.
Note:
Clearing the individual enable bits:
1. An interrupt status bit will never change from a 0 to a 1 when the corresponding individual interrupt
enable bit is cleared (set to 0), regardless of whether the limits are violated during a measurement.
2. If the individual enable bit is cleared while the associated status bit is 1, the status bit will be
cleared when the associated reading register is updated. The reading registers only get updated
when the START bit is set to ‘1’. If the enable bit is cleared when the START bit is 0, the associated
interrupt status bit will not be cleared until the start bit is set to 1 and the associated reading register
is updated.
7.2.12 Register 43h: VID
The VID register contains the values of EMC6D102 VID0-VID4 input pins. This register indicates the
status of the VID lines that interconnect the processor to the Voltage Regulator Module (VRM).
Software uses the information in this register to determine the voltage that the processor is designed
to operate at. With this information, software can then dynamically determine the correct values to
place in the Vccp Low Limit and Vccp High Limit registers.
BIT NAME R/W DEFAULT DESCRIPTION
0+12v_Error R 0 The EMC6D102 automatically sets this bit to 1 when the 12V input
voltage is less than or equal to the limit set in the 12V Low Limit register
or greater than the limit set in the 12V High Limit register.
1Reserved R 0 Reserved
2TACH1
Slow/Stalled
R 0 The EMC6D102 automatically sets this bit to 1 when the TACH1 input
reading is above the value set in the Tach1 Minimum MSB and LSB
registers.
3TACH2
Slow/Stalled
R 0 The EMC6D102 automatically sets this bit to 1 when the TACH2 input
reading is above the value set in the Tach2 Minimum MSB and LSB
registers.
4TACH3
Slow/Stalled
R 0 The EMC6D102 automatically sets this bit to 1 when the TACH3 input
reading is above the value set in the Tach3 Minimum MSB and LSB
registers.
5TACH4
Slow/Stalled
R 0 The EMC6D102 automatically sets this bit to 1 when the TACH4 input
reading is above the value set in the Tach4 Minimum MSB and LSB
registers.
6Remote
Diode 1 Fault
R 0 The EMC6D102 automatically sets this bit to 1 when there is either a
short or open circuit fault on the Remote1+ or Remote1- thermal diode
input pins as defined in the section Diode Fault on page 22.
Note: If the START bit is set and a fault condition exists, the Remote
Diode 1 reading register will be forced to 80h.
7Remote
Diode 2 Fault
R 0 The EMC6D102 automatically sets this bit to 1 when there is either a
short or open circuit fault on the Remote2+ or Remote2- thermal diode
input pins as defined in the section Diode Fault on page 22.
Note: If the START bit is set and a fault condition exists, the Remote
Diode 2 reading register will be forced to 80h.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
43h RVID0-4 RES RES RES VID4 VID3 VID2 VID1 VID0 N/A
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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DATASHEET
This register is read only – a write to this register has no effect.
7.2.13 Registers 44-4Dh: Voltage Limit Registers
Setting the Lock bit has no effect on these registers.
If a voltage input either exceeds the value set in the voltage high limit register or falls below or equals
the value set in the voltage low limit register, the corresponding bit will be set automatically by the
EMC6D102 in the interrupt status registers (41-42h). Voltages are presented in the registers at ¾ full
scale for the nominal voltage, meaning that at nominal voltage, each input will be C0h, as shown in
Table 7.5.
7.2.14 Registers 4E-53h: Temperature Limit Registers
Setting the Lock bit has no effect on these registers.
If an external temperature input or the internal temperature sensor either exceeds the value set in the
high limit register or is less than or equal to the value set in the low limit register, the corresponding
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
44h R/W 2.5V Low Limit 7 6 5 4 3 2 1 0 00h
45h R/W 2.5V High Limit 7 6 5 4 3 2 1 0 FFh
46h R/W Vccp Low Limit 7 6 5 4 3 2 1 0 00h
47h R/W Vccp High Limit 7 6 5 4 3 2 1 0 FFh
48h R/W VCC Low Limit 7 6 5 4 3 2 1 0 00h
49h R/W VCC High Limit 7 6 5 4 3 2 1 0 FFh
4Ah R/W 5V Low Limit 7 6 5 4 3 2 1 0 00h
4Bh R/W 5V High Limit 7 6 5 4 3 2 1 0 FFh
4Ch R/W 12V Low Limit 7 6 5 4 3 2 1 0 00h
4Dh R/W 12V High Limit 7 6 5 4 3 2 1 0 FFh
Table 7.5 Voltage Limits vs. Register Setting
INPUT
NOMINAL
VOLTAGE
REGISTER
SETTING AT
NOMINAL
VOLTAGE
MAXIMUM
VOLTAGE
REGISTER
SETTING AT
MAXIMUM
VOLTAGE
MINIMUM
VOLTAGE
REGISTER
SETTING AT
MINIMUM VOLTAGE
2.5V 2.5V C0h 3.32V FFh 0V 00h
Vccp 2.25V C0h 3.00V FFh 0V 00h
VCC 3.3V C0h 4.38V FFh 0V 00h
5V 5.0V C0h 6.64V FFh 0V 00h
12V 12.0V C0h 16.00V FFh 0V 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
4Eh R/W Remote Diode 1 Low Temp 7 6 5 4 3 2 1 0 81h
4Fh R/W Remote Diode 1 High Temp 7 6 5 4 3 2 1 0 7Fh
50h R/W Internal Low Temp 7 6 5 4 3 2 1 0 81h
51h R/W Internal High Temp 7 6 5 4 3 2 1 0 7Fh
52h R/W Remote Diode 2 Low Temp 7 6 5 4 3 2 1 0 81h
53h R/W Remote Diode 2 High Temp 7 6 5 4 3 2 1 0 7Fh
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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bit will be set automatically by the EMC6D102 in the Interrupt Status Register 1 (41h). For example,
if the temperature reading from the Remote1- and Remote1+ inputs exceeds the Remote Diode 1 High
Temp register limit setting, Bit[4] D1 of the Interrupt Status Register 1 will be set. The temperature limits
in these registers are represented as 8 bit, 2’s complement, signed numbers in Celsius, as shown
below in Table 7.6.
7.2.15 Registers 54-5Bh: Fan Tachometer Low Limit
Setting the Lock bit has no effect on these registers.
The Fan Tachometer Low Limit registers indicate the tachometer reading under which the
corresponding bit will be set in the Interrupt Status Register 2 register. In Auto Fan Control mode, the
fan can run at high speeds (100% duty cycle), so care should be taken in software to ensure that the
limit is low enough not to cause sporadic alerts. Note that an interrupt status event will be generated
when the tachometer reading is greater than the minimum tachometer limit.
The fan tachometer will not cause a bit to be set in the interrupt status register if the current value in
the associated Current PWM Duty registers is 00h or if the PWM is disabled via the PWM
Configuration Register.
Interrupts will never be generated for a fan if its tachometer minimum is set to FFFFh.
Table 7.6 Temperature Limits vs. Register Settings
TEMPERATURE LIMIT (DEC) LIMIT (HEX)
-127°c -127 81h
.
.
.
.
.
.
.
.
.
-50°c-50 CEh
.
.
.
.
.
.
.
.
.
0°c0 00h
.
.
.
.
.
.
.
.
.
50°c50 32h
.
.
.
.
.
.
.
.
.
127°c 127 7Fh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
54h R/W Tach1 Minimum LSB 7 6 5 4 3 2 1 0 FFh
55h R/W Tach1 Minimum MSB 15 14 13 12 11 10 9 8 FFh
56h R/W Tach2 Minimum LSB 7 6 5 4 3 2 1 0 FFh
57h R/W Tach2 Minimum MSB 15 14 13 12 11 10 9 8 FFh
58h R/W Tach3 Minimum LSB 7 6 5 4 3 2 1 0 FFh
59h R/W Tach3 Minimum MSB 15 14 13 12 11 10 9 8 FFh
5Ah R/W Tach4 Minimum LSB 7 6 5 4 3 2 1 0 FFh
5Bh R/W Tach4 Minimum MSB 15 14 13 12 11 10 9 8 FFh
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
SMSC EMC6D102 59 Revision 0.4 (04-05-05)
DATASHEET
7.2.16 Registers 5C-5Eh: PWM Configuration
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Bits [7:5] Zone/Mode
Bits [7:5] of the PWM Configuration registers associate each PWM with a temperature sensor.
■When in Auto Fan Mode, the PWM will be assigned to a zone, and its PWM duty cycle will be
adjusted according to the temperature of that zone. If ‘Hottest’ option is selected (101 or 110), the
PWM will be controlled by the hottest of zones 2 and 3, or of zones 1, 2, and 3. If one of these
options is selected, the PWM is controlled by the limits and parameters for the zone that requires
the highest PWM duty cycle, as computed by the auto fan algorithm.
■When in manual control mode, the PWMx Current Duty Cycle Registers (30h-32h) become
Read/Write. It is then possible to control the PWM outputs with software by writing to these
registers. See PWMx Current Duty Cycle Registers description.
■When the fan is disabled (100) the corresponding PWM output is driven low (or high, if inverted).
■When the fan is Full On (011) the corresponding PWM output is driven high (or low, if inverted).
Note:
■Zone 1 is controlled by Remote Diode 1 Temp Reading register
■Zone 2 is controlled by Internal Temp Reading Register
■Zone 3 is controlled by Remote Diode 2 Temp Reading register
Bit [4] PWM Invert
Bit [4] inverts the PWM output. If set to 1, 100% duty cycle will yield an output that is low for 255 clocks
and high for 1 clock. If set to 0, 100% duty cycle will yield an output that is high for 255 clocks and
low for 1 clock.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
5Ch R/W PWM 1 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h
5Dh R/W PWM 2 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h
5Eh R/W PWM 3 Configuration ZON2 ZON1 ZON0 INV RES SPIN2 SPIN1 SPIN0 62h
Table 7.7 Fan Zone Setting
ZON[7:5] PWM CONFIGURATION
000 Fan on zone 1 auto
001 Fan on zone 2 auto
010 Fan on zone 3 auto
011 Fan always on full
100 Fan disabled
101 Fan controlled by hottest of zones 2,3
110 Fan controlled by hottest of zones 1,2,3
111 Fan manually controlled
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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Bit [3] Reserved
Bits [2:0] Spin Up
Bits [2:0] specify the ‘spin up’ time for the fan. When a fan is being started from a stationary state, the
PWM output is held at 100% duty cycle for the time specified in the table below before scaling to a
lower speed.
Notes:
■During spin-up, the PWM pin is forced high for the duration of the spin-up time (i.e., 100% duty
cycle = 256/256)
■To reduce the spin-up time, this device has implemented a feature referred to as Spin Up
Reduction. Spin Up Reduction uses feedback from the tachometers to determine when each fan
has started spinning properly. Spin up for a PWM will end when the tachometer reading register is
below the minimum limit, or the spin-up time expires, whichever comes first. All tachs associated
with a PWM must be below min. for spin-up to end prematurely. This feature can be disabled by
clearing bit 4 (SUREN) of the Configuration register (7Fh). If disabled, the all fans go on full for the
duration of their associated spin up time. Note that the Tachx minimum registers must be
programmed to a value less than FFFFh in order for the spin-up reduction to work properly.
7.2.17 Registers 5F-61h: Zone Temperature Range, PWM Frequency
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
In Auto Fan Mode, when the temperature for a zone is above the Low Temperature Limit (registers
67-69h) and below the Absolute Temperature Limit (registers 6A-6Ch) the speed of a fan assigned to
that zone is determined as follows by the auto fan control logic.
When the temperature reaches the temperature value programmed in the Zone x Low Temp Limit
register, the PWM output assigned to that zone is at PWMx Minimum Duty Cycle. Between Zone x
Low Temp Limit and (Zone x Low Temp Limit + Zone x Range), the PWM duty cycle increases linearly
according to the temperature as shown in the figure below.
Table 7.8 Fan Spin-Up Register
SPIN[2:0] SPIN UP TIME
000 0 sec
001 100ms
010 250ms (default)
011 400ms
100 700ms
101 1000ms
110 2000ms
111 4000ms
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
5Fh R/W Zone 1 Range / Fan 1 Frequency RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h
60h R/W Zone 2 Range / Fan 2 Frequency RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h
61h R/W Zone 3 Range / Fan 3 Frequency RAN3 RAN2 RAN1 RAN0 RES FRQ2 FRQ1 FRQ0 C3h
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DATASHEET
Figure 7.1 Fan Activity Above Fan Temp Limit
Example for PWM1 assigned to Zone 1:
■Zone 1 Low Temp Limit (Register 67h) is set to 50°C (32h).
■Zone 1 Range (Register 5Fh) is set to 8°C (7h)
■PWM1 Minimum Duty Cycle (Register 64h) is set to 50% (80h)
In this case, the PWM1 duty cycle will be 50% at 50°C.
Since (Zone 1 Low Temp Limit) + (Zone 1 Range) = 50°C + 8°C = 58°C, the fan controlled by PWM1
will run at 100% duty cycle when the temperature of the Zone 1 sensor is at 58°C.
Since the midpoint of the fan control range is 54°C, and the median duty cycle is 75% (Halfway
between the PWM Minimum and 100%), PWM1 duty cycle would be 75% at 54°C.
Above (Zone 1 Low Temp Limit) + (Zone 1 Range), the duty cycle must be 100%.
The PWM frequency bits [2:0] determine the PWM frequency for the fan.
PWM Frequency Selection (Default =011=29.3Hz)
Range Selection (Default =1100=32×C)
Table 7.9 Register Setting vs. PWM Frequency
FREQ[2:0] PWM FREQUENCY
000 11.0 Hz
001 14.6 Hz
010 21.9 Hz
011 29.3 Hz
100 35.2 Hz
101 44.0 Hz
110 58.6 Hz
111 87.7 Hz
Temperature
Below Fan Temp Limit: Fan is off or at Fan PWM
Minimum depending on bit[7:5] of register 62h
and bit 2 of register 7Fh
Temperature LIMIT: PWM
output at MIN FAN SPEED
LIMIT+ RANGE: PWM
Output at 100% Duty
PWM Duty is linear over
this range
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Note: The range numbers will be used to calculate the slope of the PWM ramp up. For the fractional
entries, the PWM will go on full when the temp reaches the next integer value e.g., for 3.33,
PWM will be full on at (min. temp + 4).
7.2.18 Register 62h, 63h: Min/Off, PWM Ramp Rate Control
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Description of OFFx bits:
The OFFx Bits [7:5] specify whether the duty cycle will be set to 0% or the Minimum Fan Duty Cycle
when the measured temperature falls below the Temperature LIMIT register setting. OFF1 applies to
PWM1, OFF2 applies to PWM2, and OFF3 applies to PWM3.
Table 7.10 Register Setting vs. Temperature Range
RAN[3:0] RANGE (°C)
0000 2
0001 2.5
0010 3.33
0011 4
0100 5
0101 6.67
0110 8
0111 10
1000 13.33
1001 16
1010 20
1011 26.67
1100 32
1101 40
1110 53.33
1111 80
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
62h R/W Min/Off, PWM 1 Ramp Rate
Control
OFF3 OFF2 OFF1 RES RR1E RR1-2 RR1-1 RR1-0 00h
63h R/W PWM 2, PWM 3 Ramp Rate
Control
RR2E RR2-2 RR2-1 RR2-0 RR3E RR3-2 RR3-1 RR3-0 00h
Table 7.11 PWM output below Limit depending on value of Off/Min
OFF/MIN PWM ACTION
0 At 0% duty below LIMIT
1 At Min PWM Duty below LIMIT
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Description of Ramp Rate Control bits:
If the Remote1 or Remote2 pins are connected to a processor or chipset, instantaneous temperature
spikes may be sampled by the part. The auto fan control logic calculates the PWM duty cycle for all
temperature readings. If Ramp Rate Control is disabled, the PWM output will jump or oscillate
between different PWM duty cycles causing the fan to suddenly change speeds, which creates
unwanted fan noise. If enabled, the PWM Ramp Rate Control logic will prevent the PWM output from
jumping, instead the PWM will ramp up/down towards the new duty cycle at a pre-determined ramp
rate.
Ramp Rate Control
The Ramp Rate Control logic limits the amount of change to the PWM duty cycle over a period of time.
This period of time is programmable via the Ramp Rate Control bits. For a detailed description of the
Ramp Rate Control bits see Ta b l e 7 . 1 2 . For a description of the Ramp Rate Control logic see Ramp
Rate Control Logic on page 34.
Note:
■RR1E, RR2E, and RR3E enable PWM Ramp Rate Control for PWM 1, 2, and 3 respectively.
■RR1-2, RR1-1, and RR1-0 control ramp rate time for PWM 1
■RR2-2, RR2-1, and RR2-0 control ramp rate time for PWM 2
■RR3-2, RR3-1, and RR3-0 control ramp rate time for PWM 3
7.2.19 Registers 64-66h: Minimum PWM Duty Cycle
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Table 7.12 PWM Ramp Rate Control
RRX-[2:0]
PWM RAMP TIME
(SEC)
(TIME FROM 33%
DUTY CYCLE TO
100% DUTY CYCLE)
PWM RAMP TIME
(SEC)
(TIME FROM 0%
DUTY CYCLE TO
100% DUTY CYCLE)
TIME PER PWM STEP
(PWM STEP SIZE =
1/255)
PWM
RAMP RATE
(HZ)
000 35 52.53 206 msec 4.85
001 17.6 26.52 104 msec 9.62
010 11.8 17.595 69 msec 14.49
011 7.0 10.455 41 msec 24.39
100 4.4 6.63 26 msec 38.46
101 3.0 4.59 18 msec 55.56
110 1.6 2.55 10 msec 100
111 0.8 1.275 5 msec 200
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
64h R/W PWM1 Minimum Duty Cycle 7 6 5 4 3 2 1 0 80h
65h R/W PWM2 Minimum Duty Cycle 7 6 5 4 3 2 1 0 80h
66h R/W PWM3 Minimum Duty Cycle 7 6 5 4 3 2 1 0 80h
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These registers specify the minimum duty cycle that the PWM will output when the measured
temperature reaches the Temperature LIMIT register setting in Auto Fan Control Mode.
7.2.20 Registers 67-69h: Zone Low Temperature Limit
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
These are the temperature limits for the individual zones. When the current temperature equals this
limit, the fan will be turned on if it is not already. When the temperature exceeds this limit, the fan
speed will be increased according to the auto fan algorithm based on the setting in the Zone x Range
/ PWMx Frequency register. Default = 90°C=5Ah
Table 7.13 PWM Duty vs. Register Setting
MINIMUM PWM DUTY VALUE (DECIMAL) VALUE (HEX)
0% 0 00h
.
.
.
.
.
.
.
.
.
25% 64 40h
.
.
.
.
.
.
.
.
.
50% 128 80h
.
.
.
.
.
.
.
.
.
100% 255 FFh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
67h R/W Zone 1 Low Temp Limit 7 6 5 4 3 2 1 0 5Ah
68h R/W Zone 2 Low Temp Limit 7 6 5 4 3 2 1 0 5Ah
69h R/W Zone 3 Low Temp Limit 7 6 5 4 3 2 1 0 5Ah
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7.2.21 Registers 6A-6Ch: Absolute Temperature Limit
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
In Auto Fan mode, if any zone associated with a PWM output exceeds the temperature set in the
Absolute limit register, all PWM outputs will increase their duty cycle to 100% except those that are
disabled via the PWM Configuration registers. This is a safety feature that attempts to cool the system
if there is a potentially catastrophic thermal event.
If an absolute limit register set to 80h (-128°c), the safety feature is disabled for the associated zone.
That is, if 80h is written into the Zone x Temp Absolute Limit Register, then regardless of the reading
register for the zone, the fans will not turn on-full based on the absolute temp condition.
Default =100°c=64h.
When any fan is in auto fan mode, then if the temperature in any zone exceeds absolute limit, all fans
go to full, including any in manual mode, except those that are disabled. Therefore, even if a zone is
not associated with a fan, if that zone exceeds absolute, then all fans go to full. In this case, the
absolute limit can be chosen to be 7Fh for those zones that are not associated with a fan, so that the
fans won't turn on unless the temperature hits 127 degrees.
Table 7.14 Temperature Limit vs. Register Setting
LIMIT LIMIT (DEC) LIMIT (HEX)
-127°c -127 81h
.
.
.
.
.
.
.
.
.
-50°c-50 CEh
.
.
.
.
.
.
.
.
.
0°c0 00h
.
.
.
.
.
.
.
.
.
50°c50 32h
.
.
.
.
.
.
.
.
.
127°c 127 7Fh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
6Ah R/W Zone 1 Temp Absolute Limit 7 6 5 4 3 2 1 0 64h
6Bh R/W Zone 2 Temp Absolute Limit 7 6 5 4 3 2 1 0 64h
6Ch R/W Zone 3 Temp Absolute Limit 7 6 5 4 3 2 1 0 64h
Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
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7.2.22 Registers 6D-6Eh: Zone Hysteresis Registers
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
If the temperature is above the Zone x Low Temp Limit, then drops below Zone x Low Temp Limit, the
following will occur:
The fan will remain on, at Fan PWM Minimum, until the temperature goes a certain amount below the
associated zones low temperature limit (see Zone x Low Temp Limit registers). That is, when the
temperature is less than the temperature limit minus the hysteresis value, the fan will turn off.
The Hysteresis registers control this amount. See below table for details.
Table 7.15 Absolute Limit vs. Register Setting
ABSOLUTE LIMIT ABS LIMIT (DEC) ABS LIMIT (HEX)
-127°c -127 81h
.
.
.
.
.
.
.
.
.
-50°c-50 CEh
.
.
.
.
.
.
.
.
.
0°c0 00h
.
.
.
.
.
.
.
.
.
50°c50 32h
.
.
.
.
.
.
.
.
.
127°c 127 7Fh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
6Dh R/W Zone 1, Zone 2 Hysteresis H1-3 H1-2 H1-1 H1-0 H2-3 H2-2 H2-1 H2-0 44h
6Eh R/W Zone 3, Hysteresis H3-3 H3-2 H3-1 H3-0 RES RES RES RES 40h
Table 7.16 Hysteresis Settings
SETTING HYSTERESIS
0h 0°C
.
.
.
.
.
5h 5°C
.
.
.
.
.
.
Fh 15°C
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7.2.23 Register 6F: XOR Test Register
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
The part incorporates an XOR tree test mode. When the test mode is enabled by setting the ‘XEN’ bit
high via SMBus, the part enters XOR test mode.
The following signals are included in the XOR test tree:
■VID0, VID1, VID2, VID3, VID4
■TACH1, TACH2, TACH3, TACH4
■PWM2, PWM3
Since the test mode is XOR tree, the order of the signals in the tree is not important. SDA and SCL
are not included in the test tree.
7.2.24 Register 79h: SMSC Test Register
This is a read/write register. Writing this register may produce unwanted results.
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
7.2.25 Register 7Ah: SMSC Test Register
This is a read/write register. Writing this register may produce unwanted results.
7.2.26 Register 7Bh: SMSC Test Register
This is a read/write register. Writing this register may produce unwanted results.
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
6Fh R/W XOR Test Register RES RES RES RES RES RES RES XEN 00h
Register
Address
Read
/Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
79h R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
7Ah RSMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
7Bh R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 00h
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7.2.27 Register 7Ch: Special Function Register
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
This register contains the following bits:
Bit[0] Low-Power Mode Select
0= Sleep Mode (default)
1= Shutdown Mode
Bit[1] Monitoring Mode Select
0= Continuous Monitor Mode (default)
1= Cycle Monitor Mode
Bit[2] INT# Enable
0=Disables INT# pin output function (default)
1=Enables INT# pin output function
Bit[3] SMSC Reserved
This is a read/write bit. Reading this bit has no effect. Writing this bit to ‘1’ may cause unwanted
results.
Bit [4] SMSC Reserved
This is a read/write bit. Reading this bit has no effect. Writing this bit to ‘1’ may cause
unwanted results.
Bits [7:5] AVG[2:0]
The AVG[2:0] bits determine the amount of averaging for each of the six measurements that are
performed by the hardware monitor before the reading registers are updated (TABLE 22). The
AVG[2:0] bits are priority encoded where the most significant bit has highest priority. For example,
when the AVG2 bit is asserted, 32 averages will be performed for each measurement before the
reading registers are updated regardless of the state of the AVG[1:0] bits.
Note: The default for the AVG[2:0] bits is ‘010’b.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
7Ch R/W Special Function AVG2 AVG1 AVG0 SMSC SMSC INTEN MONMD LPMD 40h
Table 7.17 AVG[2:0] Bit Decoder
SFTR[7:5] AVERAGES PER READING
AVG2 AVG1 AVG0 REM DIODE 1 REM DIODE 2 INTERNAL DIODE
ALL VOLTAGE READINGS
(+2.5V, +5V, +12V, VCCP, AND VCC)
0 0 0 128 128 8 8
001 16 16 1 1
01X 16 16 16 16
1XX 32 32 32 32
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7.2.28 Register 7Eh: Interrupt Enable 1 Register
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
This register is used to enable individual voltage error events to set the corresponding status bits in
the interrupt status registers. This register also contains the group voltage enable bit (Bit[0] VOLT),
which is used to enable voltage events to force the interrupt pin (INT#) low if interrupts are enabled
(see Bit[2] INTEN of the Special Function register at offset 7Ch).
This register contains the following bits:
Bit[0] Group INT# Voltage Enable (VOLT)
0=Out-of-limit voltages do not affect the state of the INT# pin (default)
1=Enable out-of-limit voltages to make the INT# pin active low
Bit[1] Reserved
Bit[2] 2.5V Error Enable
Bit[3] Vccp Error Enable
Bit[4] Reserved
Bit[5] 5V Error Enable
Bit[6] 12V Error Enable
Bit[7] VCC Error Enable
The individual voltage error event bits are defined as follows:
0=disable
1=enable.
See Figure 5.1 Interrupt Control on page 22.
7.2.29 Register 7Fh: Configuration Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This register contains the following bits:
Bit[0] TACH3/INT# pin select: 0=TACH, 1=INT#
Bit[1] PWM2/INT# pin select: 0=PWM, 1=INT#
Bit[2] Reserved
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
7Eh R/W Interrupt Enable 1 (Voltages) VCC 12V 5V RES VCCP 25V RES VOLT ECh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
7Fh R/W Configuration INIT SMSC SMSC SUREN TRDY RES P2INT T3INT 10h
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Bit[3] TRDY: Temperature Reading Ready. This bit indicates that the temperature reading registers
have valid values. This bit is used after writing the start bit to ‘1’. 0= not valid, 1=valid.
Bit[4] SUREN: Spin-up reduction enable. This bit enables the reduction of the spin-up time based on
feedback from all fan tachometers associated with each PWM. 0=disable, 1=enable (default)
Bit[5] SMSC Reserved
This is an SMSC Reserved bit. Writing this bit to a value different than the default value may cause
unwanted results.
Bit[6] SMSC Reserved
This is an SMSC Reserved bit. Writing this bit to a value different than the default value may cause
unwanted results.
Bit[7] Initialization
Setting the INIT bit to ‘1’ performs a soft reset. This bit is self-clearing. Soft Reset sets all the registers
except the Reading Registers to their default values.
7.2.30 Register 80h: Interrupt Enable 2 Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This register is used to enable individual fan tach error events to set the corresponding status bits in
the interrupt status registers. This register also contains the group fan tach enable bit (Bit[0] TACH),
which is used to enable fan tach events to force the interrupt pin (INT#) low if interrupts are enabled
(see Bit[2] INTEN of the Special Function register at offset 7Ch).
This register contains the following bits:
Bit[0] TACH (Group TACH Enable)
0=Out-of-limit tachometer readings do not affect the state of the INT# pin (default)
1=Enable out-of-limit tachometer readings to make the INT# pin active low
Bit[1] Fan Tach 1 Event Enable
Bit[2] Fan Tach 2 Event Enable
Bit[3] Fan Tach 3 Event Enable
Bit[4] Fan Tach 4 Event Enable
Bit[5] Reserved
Bit[6] Reserved
Bit[7] Reserved
The individual fan tach error event bits are defined as follows:
0=disable
1=enable.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
80h R/W Interrupt Enable 2 (Fan
Tachs)
RES RES RES TACH4 TACH3 TACH2 TACH1 TACH 1Eh
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See Figure 5.1 Interrupt Control on page 22.
7.2.31 Register 81h: TACH_PWM Association Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This register is used to associate a PWM with a tachometer input. This association is used by the fan
logic to determine when to prevent a bit from being set in the interrupt status registers.
The fan tachometer will not cause a bit to be set in the interrupt status register:
a. if the current value in Current PWM Duty registers is 00h or
b. if the fan is disabled via the Fan Configuration Register.
Note: A bit will never be set in the interrupt status for a fan if its tachometer minimum is set to FFFFh.
See bit definition below.
Bits[1:0] Tach1. These bits determine the PWM associated with this Tach. See bit combinations below.
Bits[3:2] Tach2. These bits determine the PWM associated with this Tach. See bit combinations below.
Bits[5:4] Tach3. These bits determine the PWM associated with this Tach. See bit combinations below.
Bits[7:6] Tach4. These bits determine the PWM associated with this Tach. See bit combinations below.
Notes:
■Any PWM that has no TACH inputs associated with it must be configured to operate in Mode 1.
■All TACH inputs must be associated with a PWM output. If the tach is not being driven by the
associated PWM output it should be configured to operate in Mode 1 and the associated TACH
interrupt must be disabled.
7.2.32 Register 82h: Interrupt Enable 3 Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This register is used to enable individual thermal error events to set the corresponding status bits in
the interrupt status registers. This register also contains the group thermal enable bit (Bit[0] TEMP),
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
81h R/W TACH_PWM Association T4H T4L T3H T3L T2H T2L T1H T1L A4h
Bits[1:0], Bits[3:2], Bits[5:4], Bits[7:6] PWM Associated With Tachx
00 PWM1
01 PWM2
10 PWM3
11 Reserved
Register
Address
Read/
Write
Register
Name
Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
82h R/W Interrupt Enable 3 (Temp) RES RES RES RES D2EN D1EN AMB TEMP 0Eh
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DATASHEET
which is used to enable thermal events to force the interrupt pin (INT#) low if interrupts are enabled
(see Bit[2] INTEN of the Special Function register at offset 7Ch).
This register contains the following bits:
Bit[0] TEMP. Group temperature enable bit.
0=Out-of-limit temperature readings do not affect the state of the INT# pin (default)
1=Enable out-of-limit temperature readings to make the INT# pin active low
Bit[1] Ambient Temperature Status Enable bit.
Bit[2] Remote Diode 1 Temperature Status Enable bit.
Bit[3] Remote Diode 2 Temperature Status Enable bit
Bit[4] Reserved
Bit[5] Reserved
Bit[6] Reserved
Bit[7] Reserved
The individual thermal error event bits are defined as follows:
0=disable
1=enable.
See Figure 5.1 Interrupt Control on page 22.
7.2.33 Registers 85h-88h: A/D Converter LSbs Registers
There is a 10-bit Analog to Digital Converter (ADC) located in the hardware monitoring block that
converts the measured voltages into 10-bit reading values. Depending on the averaging scheme
enabled, the hardware monitor may take multiple readings and average them to create the values
stored in the reading registers (i.e., 16x averaging, 32x averaging, etc.) The 8 MSb’s of the reading
values are placed in the Reading Registers. When the upper 8-bits located in the reading registers
are read the 4 LSb’s are latched into their respective bits in the A/D Converter LSbs Register. This
give 12-bits of resolution with a minimum value of 1/16th per unit measured. (i.e., Temperature Range:
-127.9375 ºC < Temp < 127.9375 ºC and Voltage Range: 0 < Voltage < 256.9375) . See the DC
Characteristics for the accuracy of the reading values.
The eight most significant bits of the 12-bit averaged readings are stored in Reading registers and
compared with Limit registers. The Interrupt Status Register bits are asserted if the corresponding
measured value(s) on the inputs violate their programmed limits.
Register
Address
Read/
Write
Register
Name
Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
85h R A/D Converter LSbs Reg 1 RD2.3 RD2.2 RD2.1 RD2.0 RD1.3 RD1.2 RD1.1 RD1.0 N/A
86h R A/D Converter LSbs Reg 2 V12.3 V12.2 V12.1 V12.0 AM.3 AM.2 AM.1 AM.0 N/A
87h R A/D Converter LSbs Reg 3 V50.3 V50.2 V50.1 V50.0 V25.3 V25.2 V25.1 V25.0 N/A
88h R A/D Converter LSbs Reg 4 VCC.3 VCC.2 VCC.1 VCC.0 VCP.3 VCP.2 VCP.1 VCP.0 N/A
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DATASHEET
7.2.34 Register 89h: SMSC Test Register
7.2.35 Registers 8Ah: SMSC Test Register
7.2.36 Registers 8Bh: SMSC Test Register
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
This register must not be written. Writing this register may produce unexpected results.
7.2.37 Registers 8Ch: SMSC Test Register
7.2.38 Registers 8Dh: SMSC Test Register
This register becomes read only when the Lock bit is set. Any further attempts to write to this register
shall have no effect.
This register must not be written. Writing this register may produce unexpected results.
7.2.39 Registers 8Eh: SMSC Test Register
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
89h RSMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
8Ah RSMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 4Dh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
8Bh R/W SMSC Test Register RES TST6 TST5 TST4 TST3 TST2 TST1 TST0 4Dh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
8Ch RSMSC Test Register RES RES RES TST4 TST3 TST2 TST1 TST0 0Eh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
8Dh R/W SMSC Test Register RES RES RES TST4 TST3 TST2 TST1 TST0 0Eh
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
8Eh R SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A
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This register is an SMSC Test register.
7.2.40 Registers 90h-93h: TachX Option Registers
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Bit[0] SLOW
1= Force tach reading register to FFFFh if number of tach edges detected is greater than 0, but less
than programmed number of edges. (default)
0=Force tach reading register to FFFEh if number of tach edges detected is greater than 0, but less
than programmed number of edges.
Bit[2:1] The number of edges for tach1 reading:
00=2 edges
01=3 edges
10=5 edges (default)
11=9 edges
Bit[3] Tachometer Reading Mode
0=mode 1 – standard
1=mode 2 – enhanced. (default)
Bit[4] Tach (Mode 2 only)
0=Don’t ignore first 3 edges (default)
1=Ignore first 3 tachometer edges after guard time
Note: This bit has been added to support a small sampling of fans that emit irregular tach pulses
when the PWM transitions ‘ON’. Typically, the guard time is sufficient for most fans.
Bit[7:5] PWM max stretching time
000=disable stretching
001=50msec
010=100msec
011=200msec
100=400msec
101=600msec
110=800msec (default)
111=950msec
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
90h R/W Tach1 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh
91h R/W Tach2 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh
92h R/W Tach3 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh
93h R/W Tach4 Option STCH2 STCH1 STCH0 3EDG MODE EDG1 EDG0 SLOW CCh
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Note: PWM Max stretch time determines the maximum time for monitoring the tach input. If
stretching is disabled, the tach will only be monitored when the PWM duty cycle is ‘ON’. For
a complete definition of stretching see section PWM Stretching on page 38.
7.2.41 Registers 94h-96h: PWMx Option Registers
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Bits[1:0] Tachs reading registers associated with PWMx are updated: (Mode 2 only)
00=once a second (default)
01=twice a second
1x=every 300msec
Bit[2] Snap to Zero (SZEN)
This bit determines if the PWM output ramps down to OFF or if it is immediately set to zero.
0=Step Down the PWMx output to Off at the programmed Ramp Rate
1=Transition PWMx to Off immediately when the calculated duty cycle is 00h (default)
Bit[4:3] Guard time (Mode 2 only)
00=63 clocks (90kHz clocks ~ 700usec)
01=32 clocks (90kHz clocks ~ 356usec) (default)
10=16 clocks (90kHz clocks ~ 178usec)
11=8 clocks (90kHz clocks ~ 89usec)
Bit[5] Opportunistic Mode Enable
0= Opportunistic Mode Disabled. Update Tach Reading once per PWMx Update Period (see Bits[1:0]
in this register)
1=Opportunistic Mode is Enabled. The tachometer reading register is updated any time a valid
tachometer reading can be made without stretching the PWM output signal. If a valid reading is
detected prior to the Update cycle, then the Update counter is reset.
Bit[7:6] Reserved
7.2.42 Register 97h: SMSC Test Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
Register
Address
Read/
Write
Register
Name
Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
94h R/W PWM1 Option RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
95h R/W PWM2 Option RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
96h R/W PWM3 Option RES RES OPP GRD1 GRD0 SZEN UPDT1 UPDT0 0Ch
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
97h R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 5Ah
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This is an SMSC Test Register. Writing to this register may cause unwanted results.
7.2.43 Register 98h:SMSC Test Register
These registers become read only when the Lock bit is set. Any further attempts to write to these
registers shall have no effect.
This is an SMSC Test Register. Writing to this register may cause unwanted results.
7.2.44 Register FFh: SMSC Test Register
This register is an SMSC Test register.
Register
Address
Read/
Write Register Name Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
98h R/W SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0
glitch
F1h
Register
Address
Read/
Write
Register
Name
Bit 7
(MSb) Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
(LSb)
Default
Value
98h R SMSC Test Register TST7 TST6 TST5 TST4 TST3 TST2 TST1 TST0 N/A
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DATASHEET
Chapter 8 Operational Description
8.1 Maximum Guaranteed Ratings
Note: Stresses above those listed could cause permanent damage to the device. This is a stress
rating only and functional operation of the device at any other condition above those indicated
in the operation sections of this specification is not implied. When powering this device from
laboratory or system power supplies, it is important that the Absolute Maximum Ratings not be
exceeded or device failure can result. Some power supplies exhibit voltage spikes on their
outputs when the AC power is switched on or off. In addition, voltage transients on the AC
power line may appear on the DC output. If this possibility exists, it is suggested that a clamp
circuit be used.
8.2 Ratings for Operation
TA = 0oC - 70oC, VCC=+3.3V±10%
PARAMETER MAXIMUM VALUE
Operating Temperature Range 0oC to +70oC
Storage Temperature Range -55o to +150oC
Lead Temperature Range Refer to JEDEC Spec. J-STD-020
Maximum Vcc +5.5V
Positive Voltage on any pin (except for analog inputs), with respect to Ground Vcc+0.3V
Negative Voltage on any pin (except for analog inputs), with respect to Ground -0.3V
PARAMETER SYMBOL MIN TYP MAX UNITS COMMENTS
Temperature-to-Digital
Converter Characteristics
Internal Temperature
Accuracy
External Diode Sensor
Accuracy
-3
-2
-5
-3
±0.25
±0.25
+3
+2
+5
+3
oC
oC
oC
oC
oC
oC
0oC <= TA <= 70oC
40oC <= TA <= 70oC
Resolution
-40oC <= TS <= 125oC
40oC <= TS <= 100oC
Resolution
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Notes:
■Voltages are measured from the local ground potential, unless otherwise specified.
■Typical values are at TA=25°C and represent most likely parametric norm.
■The maximum allowable power dissipation at any temperature is PD = (TJmax - TA) / QJA.
Analog-to-Digital Converter
Characteristics
Total Unadjusted Error
Differential Non-Linearity
Power Supply Sensitivity
Total Monitoring Cycle Time
(Cycle Mode, Default
Averaging)
Conversion Time
(Continuous Mode, Default
Averaging)
Input Resistance
ADC Resolution
TUE
DNL
PSS
tC(Cycle)
tC(Cts) 203
±1
±1
1.22
223
140
±2
1.4
248
200
%
LSB
%/V
sec
msec
kΩ
Note 8.1
Note 8.2
Note 8.3
10 bits Note 8.6
Input Buffer
(VID0-VID4,TACH1-TACH4)
Low Input Level
High Input Level
VILI
VIHI 2.0
0.8
Vcc+0.3
V
V
IOD Type Buffer
(SCL, SDA, PWM1, PWM2,
PWM3/ADDRESS ENABLE,
INT#
Low Input Level
High Input Level
Hysteresis
Low Output Level
VILI
VIHI
VHYS
VOL
2.0
500
0.8
Vcc+0.3
0.4
V
V
mV
VIOL = +4.0 mA (Note 8.5)
Leakage Current
(ALL - Digital)
Input High Current
Input Low Current
Digital Input Capacitance
ILEAKIH
ILEAKIL
CIN
10
-10
10
µA
µA
pF
(Note 8.4)
VIN = VCC
VIN = 0V
VCC Supply Current
Active Mode
Sleep Mode
Shutdown Mode
ICC
ICC
ICC
3
500
3
mA
µA
µA
All outputs open, all
inputs transitioning
from/to 0V to/from 3.3V.
PARAMETER SYMBOL MIN TYP MAX UNITS COMMENTS
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DATASHEET
■Timing specifications are tested at the TTL logic levels, VIL=0.4V for a falling edge and VIH=2.4V
for a rising edge. TRI-STATE output voltage is forced to 1.4V.
Note 8.1 TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC.
Note 8.2 Total Monitoring Cycle Time for cycle mode includes a one second delay plus all
temperature conversions and all analog input voltage conversions.
Note 8.3 See Table 5.2, “Conversion Cycle Timing,” on page 19 for conversion cycle timing for all
averaging options. Only the nominal default case is shown in this section.
Note 8.4 All leakage currents are measured with all pins in high impedance.
Note 8.5 The low output level for PWM pins is actually +8.0mA.
Note 8.6 The h/w monitor analog block implements a 10-bit ADC. The output of this ADC goes to
an averager block, which can be configured to accumulate the averaged value of the
analog inputs. The amount of averaging is programmable. The output of the averaging
block produces a 12-bit temperature or voltage reading value. The 8 MSbits go to the
reading register and the 4 LSbits to the A/D LSb register.
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Chapter 9 Timing Diagrams
9.1 PWM Outputs
The following section shows the timing for the PWM[1:3] outputs.
Figure 9.1 PWMx Output Timing
Note 9.1 This value is programmable by the PWM frequency bits located in the FRFx registers.
Note 9.2 The PWM High Time is based on a percentage of the total PWM period (min=0/256*TPWM,
max =255/256*TPWM). During Spin-up the PWM High Time can reach a 100% or Full On.
(TPWM = t1).
9.2 SMBus Interface
Figure 9.2 SMBus Timing
Table 9.1 Timing for PWM[1:3] Outputs
NAME DESCRIPTION MIN TYP MAX UNITS
t1 PWM Period (Note 9.1)11.4 90.9 msec
t2 PWM High Time (Note 9.2) 0 99.6 %
t1
t2
FANx
PS S P
tBUF
tHD:STA
tLOW
tSU:DAT tSU:STA
tHD:STA tSU:STO
tHIGH
tHD:DAT
tF
tR
SCLK
SDAT
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Note 9.3 The SMBus timing (e.g., max clock frequency of 400kHz) specified exceeds that specified
in the System Management Bus Specification, Rev 1.1. This corresponds to the maximum
clock frequency for fast mode devices on the I2C bus. See “The I2C Bus Specification,”
version 2.0, Dec. 1998.
Note 9.4 At 400kHz, spikes of a maximum pulse width of 50ns must be suppressed by the input
filter.
Note 9.5 If using 100 kHz clock frequency, the next data bit output to the SDA line will be 1250 ns
(1000 ns (TR max) + 250 ns (TSU:DAT min) @ 100 kHz) before the SCLK line is released.
SYMBOL PARAMETER
LIMITS
UNITS COMMENTSMIN MAX
Fsmb SMB Operating Frequency 10 400 kHz Note 9.3
Tsp Spike Suppression 50 ns Note 9.4
Tbuf Bus free time between Stop and Start
Condition
1.3 µs
Thd:sta Hold time after (Repeated) Start Condition.
After this period, the first clock is
generated.
0.6 µs
Tsu:sta Repeated Start Condition setup time 0.6 µs
Tsu:sto Stop Condition setup time 0.6 µs
Thd:dat Data hold time 0.3 0.9 µs
Tsu:dat Data setup time 100 ns Note 9.5
Tlow Clock low period 1.3 µs
Thigh Clock high period 0.6 µs
Tf Clock/Data Fall Time 20+0.1Cb300 ns
Tr Clock/Data Rise Time 20+0.1Cb300 ns
CbCapacitive load for each bus line 400 pF
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Chapter 10 Mechanical Specifications
Figure 10.1 24-Pin SSOP Package Outline, 0.150 Wide Body, 0.025 Pitch
Table 10.1 24-pin SSOP Package Parameters
Notes:
1. Controlling Unit: inch.
2. Tolerance on the true position of the leads is ± 0.0035 inches maximum.
3. Package body dimensions D and E1 do not include the mold protrusion. Maximum mold protrusion
is 0.006 inches for ends, and 0.010 inches for sides.
4. Dimension for foot length L measured at the gauge plane 0.010 inches above the seating plane.
5. Details of pin 1 identifier are optional but must be located within the zone indicated.
MIN NOMINAL MAX REMARKS
A0.053 ~ 0.069 Overall Package Height
A1 0.004 ~ 0.010 Standoff
A2 ~ ~ 0.061 Body Thickness
D0.337 ~ 0.344 X Body Size
E0.228 ~ 0.244 Y Span
E1 0.150 ~ 0.157 Y body Size
H0.007 ~ 0.010 Lead Frame Thickness
L0.016 0.025 0.050 Lead Foot Length
e0.025 Basic Lead Pitch
è0o~8
oLead Foot Angle
W0.008 0.010 0.012 Lead Width
ccc ~ ~ 0.004 Coplanarity
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DATASHEET
Appendix A ADC Voltage Conversion
Table A.1 Analog-to-Digital Voltage Conversions for Hardware Monitoring Block
INPUT VOLTAGE A/D OUTPUT
12 VIN 5 VIN VCC 2.5 VIN VCCPIN Decimal Binary
<0.062 <0.026 <0.0172 <0.013 <0.012 0 0000 0000
0.062–0.125 0.026–0.052 0.017–0.034 0.013–0.026 0.012–0.023 1 0000 0001
0.125–0.188 0.052–0.078 0.034–0.052 0.026–0.039 0.023–0.035 2 0000 0010
0.188–0.250 0.078–0.104 0.052–0.069 0.039–0.052 0.035–0.047 3 0000 0011
0.250–0.313 0.104–0.130 0.069–0.086 0.052–0.065 0.047–0.058 4 0000 0100
0.313–0.375 0.130–0.156 0.086–0.103 0.065–0.078 0.058–0.070 5 0000 0101
0.375–0.438 0.156–0.182 0.103–0.120 0.078–0.091 0.070–0.082 6 0000 0110
0.438–0.500 0.182–0.208 0.120–0.138 0.091–0.104 0.082–0.093 7 0000 0111
0.500–0.563 0.208–0.234 0.138–0.155 0.104–0.117 0.093–0.105 8 0000 1000
…………………
4.000–4.063 1.666–1.692 1.100–1.117 0.833–0.846 0.749–0.761 64 (1/4 Scale) 0100 0000
…………………
8.000–8.063 3.330–3.560 2.200–2.217 1.667–1.680 1.499–1.511 128 (1/2
Scale)
1000 0000
…………………
12.000–
12.063
5.000–5.026 3.300–3.317 2.500–2.513 2.249–2.261 192 (3/4
Scale)
1100 0000
…………………
15.312–
15.375
6.380–6.406 4.210–4.230 3.190–3.203 2.869–2.881 245 1111 0101
15.375–
15.437
6.406–6.432 4.230–4.245 3.203–3.216 2.881–2.893 246 1111 0110
15.437–
15.500
6.432–6.458 4.245–4.263 3.216–3.229 2.893–2.905 247 1111 0111
15.500–
15.563
6.458–6.484 4.263–4.280 3.229–3.242 2.905–2.916 248 1111 1000
15.625–
15.625
6.484–6.510 4.280–4.300 3.242–3.255 2.916–2.928 249 1111 1001
15.625–
15.688
6.510–6.536 4.300–4.314 3.255–3.268 2.928–2.940 250 1111 1010
15.688–
15.750
6.536–6.562 4.314–4.330 3.268–3.281 2.940–2.951 251 1111 1011
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DATASHEET
15.750–
15.812
6.562–6.588 4.331–4.348 3.281–3.294 2.951–2.964 252 1111 1100
15.812–
15.875
6.588–6.615 4.348–4.366 3.294–3.307 2.964–2.975 253 1111 1101
15.875–
15.938
6.615–6.640 4.366–4.383 3.307–3.320 2.975–2.987 254 1111 1110
>15.938 >6.640 >4.383 >3.320 >2.988 255 1111 1111
Table A.1 Analog-to-Digital Voltage Conversions for Hardware Monitoring Block (continued)
INPUT VOLTAGE A/D OUTPUT
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Appendix B Example Fan Circuits
The following figures show examples of circuitry on the board for the PWM outputs, tachometer inputs,
and remote diodes. Figure B.1 shows how the part can be used to control four fans by connecting two
fans to one PWM output.
Note: These examples represent the minimum required components. Some designs may require
additional components.
Figure B.1 Fan Drive Circuitry (Apply to PWM Driving Two Fans)
Figure B.2 Fan Drive Circuitry (Apply to PWM Driving One Fan)
MMBT3904
MMBT2222
MMBT2222
10
10
2.2k
1k
3.3V3.3V
Fan1
Fan2
M
M
12
V
PWMx
Empty
Empty
MMBT2222
0
470
3.3V
Fan
M
12V
PWMx
Empty
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Figure B.3 Fan Tachometer Circuitry (Apply to Each Fan)
Figure B.4 Remote Diode (Apply to Remote2 Lines)
Notes:
1. 2.2nF cap is optional and should be placed close to the EMC6D102 if used.
2. The voltage at PWM3 must be at least 2.0V to avoid triggering Address Enable.
3. The Remote Diode + and Remote Diode - tracks should be kept close together, in parallel with
grounded guard tracks on each side. Using wide tracks will help to minimize inductance and
reduce noise pickup. A 10 mil track minimum width and spacing is recommended. See Figure B.5,
"Suggested Minimum Track Width and Spacing".
.
Figure B.5 Suggested Minimum Track Width and Spacing
Note: For fans controlled directly by a PWM, it is suggested to implement
the optional diode (D1) to protect the tachometer input from large voltage
spikes generated by the fan.
10k
3.3V
Tach
Output
from Fan
TACH
Input
D1
IN4148
Remote Diode +
Remote Diode -
2.2nF
External Temperature
Sensing Diode
(MMBT3904)
GND
GND
D+
D-
10 mil.
10 mil.
10 mil.
10 mil.
10 mil.
10 mil.
10 mil.
