General Description
The DS28DG02 evaluation system (EV system) consists
of an evaluation board (EV board) and a Maxim
CMAXQUSB command module. The EV board is a
daughter card for the command module. PC connectivi-
ty is included in the kit and free evaluation software is
available for download from the web page listed in
Support Resources
. The DS28DG02 is a mixed-signal
memory device. It contains 2Kb of EEPROM memory,
along with PIO, real-time clock (RTC), reset, battery
monitor, and watchdog functions. Communication to the
device is through the industry-standard Serial Peripheral
Interface (SPI™)interface. The evaluation software runs
under 32-bit Windows Vista®, XP, 2000, and 98SE oper-
ating systems, providing a handy user interface to exer-
cise the DS28DG02 features.
Support Resources
1) DS28DG02 EV Kit Data Sheet and Software:
www.maxim-ic.com/DS28DG02EVKit
2) User’s Guide to the DS28DG02:
www.maxim-ic.com/AN4040
3) Application Note 3601:
Troubleshooting Windows
Plug-and-Play and USB for Maxim Evaluation Kits
:
www.maxim-ic.com/AN3601
4) Listing of All Multifunction Memory EV Kits:
www.maxim-ic.com/memoryEVKits
5) Technical Support:
www.maxim-ic.com/support
Features
♦Proven PCB Layout
♦Complete Evaluation System
♦Convenient On-Board Test Points
♦Easy Setup
♦PC Connectivity Included
♦Free Downloadable Evaluation Software Available
Evaluates: DS28DG02
________________________________________________________________
Maxim Integrated Products
1
Rev 1; 5/08
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
PART TYPE
DS28DG02EVKIT EV Kit
EV Kit Contents
DESIGNATION QTY DESCRIPTION
H1 4
2-pin shunts (for jumpering)
Tyco/Amp 881545-2
H2 1
Small antistatic bag to hold H1
shunts
H3 1 DS28DG02 EV board
H4 1
Small antistatic bag to hold
EV board
H5 1 Instruction sheet
H6 1
Box and packaging material to hold
bagged EV board, bag of shunts,
and instruction sheet (H1–H5)
H7 1
Boxed CMAXQUSB command
module with USB cable
H8 1
Box and packaging material to
hold EV kit contents (H1–H7)
SPI is a trademark of Motorola, Inc.
Windows Vista is a registered trademark of Microsoft Corp.
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
2 _______________________________________________________________________________________
Component List
DESIGNATION QTY DESCRIPTION SUPPLIER/PART NUMBER
B1 1 3V lithium 16mm coin battery with solderable tabs Panasonic BR1632A/HA
C1, C2 2 0.1μF SMT capacitors (1206) KMET C1206C104K1RACTU
D1, D6, D7 3 SMT red LEDs (1206) LiteOn LTST-C150CKT
D2–D5 4 SMT green LEDs (1206) LiteOn LTST-C150GKT
J1 1 100-mil centers, square-post, 2-pin terminal strip Molex 22-28-4022
J2 1
100-mil centers, 40-pin (dual-row) female,
right-angle header
Available from the following suppliers:
Methode (Adam Tech) RS2R-40-G
Oupiin 2044-2X20GRSN
Samtec SSW-120-02-S-D-RA
J3–J4 2 100-mil centers, square-post, 3-pin terminal strip Molex 22-28-4032
J6 1
100-mil centers, square-post, 12-pin terminal strip
right angle Molex 22-28-8120
R1 1 SMT 500 ±1% resistor (1206) ROHM MCR18EZHF4990
R2 1
100 mechanical potentiometer through-mount,
3-pin
Available from the following suppliers:
Copal Electronics CT6EP101
Murata PVC6A101C01B00
R3, R8, R9 3 10k resistors (1206) Panasonic-ECG ERJ-8ENF1002V
R5 1
Through-mount, 3-pin 500 mechanical
potentiometer
Available from the following suppliers:
Copal Electronics CT6EP501
Murata PVC6A501C01B00
R6 1 SMT 250 ±1% resistor (1206) ROHM MCR18EZHF2490
R7 1 SMT 470 resistor (1206) Panasonic-ECG ERJ-8ENF4700V
RP1 1 1kresistor pack, 9 res, 10-pin CTS Corporation 770101102P
RP2 1 100k resistor pack, 9 res, 10-pin CTS Corporation 770101104P
RP3 1 470 resistor pack, 9 res, 10-pin CTS Corporation 770101471P
SB1 1 Jumper block with 8 built-in switches, 16-pin DIP Grayhill Incorporated 76SB08ST
SW1 1 Momentary pushbutton switch Panasonic-ECG EVQ-PJA04Q
TP1, TP2 2 Test points Keystone 5011
U1 1
2Kb SPI EEPROM with PIO, RTC, reset, battery
monitor and watchdog (4.4mm 28-pin TSSOP) Maxim DS28DG02E-3C+
X1 1 32kHz time crystal Citizen CFS145-32.768KDZF-UB
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
_______________________________________________________________________________________ 3
Figure 1. DS28DG02 EV Board
Figure 2. DS28DG02 EV Board Connected to CMAXQUSB
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
Quick Start
Note: In the following sections software-related items are
identified by bolding. Text in bold refers to items directly
from the EV kit software. Items in bold and underline
refer to items from the Windows operating system.
1) Before beginning, make sure the following equip-
ment is available:
• DS28DG02 (contains DS28DG02 EV board and
CMAXQUSB module).
• Computer with a Windows Vista/XP/2000/98SE
operating system with a spare USB port.
2) Do the following before connecting to the PC:
• Select 3.3V logic by setting the CMAXQUSB
VDD SELECT jumper.
• Set up the EV board by placing a jumper on the
J3 jumper block (J3 BATT SRC). If you wish to
evaluate the battery monitor function, choose VCC
to prevent the battery from prematurely draining.
Also, place a jumper on the J1 RESET ENABLE
pins, along with a jumper on J4 WPZ INPUT
(preferably in the rightmost position to prevent
accidental write protection of the SPI Status Byte).
• Connect the EV board to the CMAXQUSB board
with the 40-pin connector at location P4 (the SPI
pins). See Figure 2 for proper EV board orienta-
tion (component side up) when connecting the
EV board to the CMAXQUSB board.
3) Download the evaluation software from the EV kit’s
Quick View: www.maxim-ic.com/DS28DG02EVKit.
The evaluation software is provided as a *.zip
archive file. Unzip the archive’s contents into an
empty or newly created directory.
4) Connect the USB cable between the CMAXQUSB
and the computer. When you plug in the
CMAXQUSB board for the first time, the Windows
plug-and-play system detects the new hardware
and automatically runs the Add New Hardware
Wizard. Be sure to specify the search location for
the device driver, which is the directory where the
evaluation software files were unzipped.
5) During device driver installation, Windows displays
a warning message indicating that the device driver
for the CMAXQUSB board does not contain a digital
signature. This is not an error condition. It is safe to
proceed with the installation.
6) If any problems occur during device driver installa-
tion, refer to Application Note 3601
: Troubleshooting
Windows Plug-and-Play and USB for Maxim
Evaluation Kits
for more details.
7) The Microsoft .NET framework Version 1.1 is
required for the program to run. To verify if it is
installed, look in Control Panel under Add/Remove
Software for a listing. If no listing is found, go to
www.microsoft.com and perform a site search for
.NET 1.1 redistributable. Click on the first item in
the results list. It should contain download and
installation instructions.
8) Start the EV kit software by double-clicking the file,
DS28DG02_Evaluation_Program.exe,
in the file fold-
er containing the unzipped evaluation software files.
Detailed Description of
Software
Figure 3 shows the DS28DG02 software program’s
main window. Note that it consists of seven tabs, with
each tab offering the ability to exercise a group of relat-
ed DS28DG02 functional blocks. The sections are: SPI,
R/W, UserEE, MFC/MFS, GPIO, RTC, and WatchDog.
Each of these tabs is described in this section.
Note that a status pane exists at the very bottom of the
window. The left-hand side gives the firmware string of
the CMAXQUSB board (if connected), and the right-
hand side gives status information (in the form of a
small string) on the success or failure of the last opera-
tion attempted.
SPI
See Figure 3 for a screenshot of the SPI tab. This tab
allows the user to input raw SPI commands and com-
municate to the DS28DG02 through this low-level serial
protocol. The user can assert the chip select (CS) pin
to enable communication to the device, and send data
to the chip by inputting data into the master-out, slave-
in (MOSI) text box and clicking the Execute SPI Comm
button. MOSI is also read out from the chip during the
data exchange.
R/W
Figure 4 shows a screenshot of the R/W tab. This tab
exercises raw read and write functions. Be careful
using this tab as the reading/writing extends to PIO and
control/status registers. To use, simply give the starting
address from which to perform the memory operation
and the number of bytes to read or write. If performing
a write operation, input the data to write in hexadecimal
form (with a space between bytes) in the text box. Next,
choose the type of operation (Read Op or Write Op),
and click the Execute Memory Op button to perform
the action. For reading and writing the user EEPROM
areas, see the
UserEE
section.
4 _______________________________________________________________________________________
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
_______________________________________________________________________________________ 5
Figure 3. DS28DG02 Evaluation Software: Main Window
Figure 4. DS28DG02 Evaluation Software: R/W Tab
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
6 _______________________________________________________________________________________
UserEE
Figure 5 shows the UserEE tab. It allows a safe way to
read and write to the user EEPROM memory areas of
the DS28DG02. To use, first input which 64-byte block
of EEPROM memory is read or written into the General
Memory Block spin box. Valid numbers are 0, 1, 2, or
3. Next, choose the format type of the data to be dis-
played in the text box after a read operation or inputted
before a write operation. The choices are ASCII or hex.
Finally, choose which memory operation is desired by
clicking on either the Read User EEPROM or Write
User EEPROM buttons. Prior to writing to the part,
make sure the data to write has been successfully
entered into the text box in the correct format, either
ASCII (no spaces) or hex (space between each byte).
Figure 5. DS28DG02 Evaluation Software: UserEE Tab
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
_______________________________________________________________________________________ 7
Figure 6. DS28DG02 Evaluation Software: MFC/MFS Tab
MFC/MFS
The MFC/MFS tab allows the user to read the status
register for alarms and flags and write to the control
register to enable the various monitors and timers and
change other hardware settings. It also allows for exer-
cising the SPI status register, which gives status on
blocks of EEPROM memory that are write protected
and specifies the duration of the watchdog timeout.
See Figure 6 for a screenshot.
This tab is used extensively when experimenting with
nonmemory functions of the DS28DG02, such as volt-
age monitor, watchdog, write protect, and RTC func-
tions. To use the tab, start by reading the registers to
see which flags and alarms have been set. Clicking the
Read MFC/MFS button and the Read button in the SPI
Status Byte section retrieves them. Once all the flags,
alarms, and settings have been retrieved, the
DS28DG02 can be reconfigured to the desired settings
and any alarm conditions can be cleared.
DS28DG02 Evaluation Board/Evaluation System
The MFC/MFS tab is divided into two sections: the
Multifunction Registers section and the SPI Status
Byte section. In the Multifunction Registers section,
the left-hand side of the tab shows the control register’s
settings. To set these, just click in the checkbox next to
the appropriate label. The last setting does not contain a
checkbox, but rather, a listbox of four settings for the
battery trip point (BTRP). Highlight the desired BTRP
setting by clicking on it. See Table 1 for a list of control
settings. Clicking on the MFC settings automatically
writes the new setting to the part. A checkmark means a
1 has been written to the register bit, enabling the fea-
ture, and no checkmark means that a 0 has been written
to the register bit, disabling the feature. The BTRP has
four possible settings (requiring 2 bits). See Table 1 for
a list of the possible battery monitor trip points. An alter-
nate way to change the control register settings
(besides clicking the checkboxes) is to calculate the
byte value in hex of the control register, which consists
of a single byte. See the BITS column of Table 1, keep-
ing in mind a check is a 1 and an uncheck is a 0. After
calculating this number, input it into the Control text box
and click the Write MFC button.
Evaluates: DS28DG02
8 _______________________________________________________________________________________
Table 1. Control Register Settings
SETTING BITS DEFINITION
CAE: Clock Alarm Enable b0
Enable/disable control of the RTC/calendar alarm.
check: enable
uncheck: disable (power-on default)
OSCE: RTC Oscillator Enable b1
Run/halt control of the RTC’s 32kHz oscillator.
check: enable
uncheck: disable (power-on default)
WDE: Watchdog Enable b2
Enable/disable control of the watchdog and its alarm.
check: enable
uncheck: disable (power-on default)
WDOS: Watchdog Output
Selection b3
Pin selection for watchdog alarm signaling.
check: ALMZ pin (lights red D6 LED)
uncheck: WDOZ pin (lights red D7 LED) (power-on default)
BTRP: Battery Monitor Trip Point b[5:4]
Selection of the nominal BTRP voltage. Select one of the following:
b00 1.75V (power-on default)
b01 2.00V
b10 2.25V
b11 2.50V
BME: Battery Monitor Enable b6
Enable/disable control of the battery monitor and its alarm.
check: enable
uncheck: disable (power-on default)
Notes:
1. The battery test takes place:
a) after BME changes to 1
b) after VCC ramps up
c) every hour on the hour
2. The RTC must be running (OSCE enabled) for the battery monitor to function.
DS28DG02 Evaluation Board/Evaluation System
The other half of the Multifunction Registers section of
the MFC/MFS tab consists of the DS28DG02’s status
register. Similar to the control register, a list of check-
boxes are listed. A checkmark means an alarm or flag
is set or active (giving a 1) and no checkmark means
that the alarm or flag is not active (giving a 0). See
Table 2 for a list of status register alarms and status
flags. As with the control register, the status register is
a single byte, with individual alarms and status flags
taking up single bits. So, clicking on the Read
MFC/MFS button gives a hex number representing the
entire status byte. This number is displayed in the
Status text box. Translating this number to binary gives
the indvidual alarms/flags of the status register. See the
BITS column in Table 2 for the bit designator. Note that
writing to the control register, except for the WPZV sta-
tus flag, clears all alarms/flags, and that when an alarm
or flag is set, the MFC/MFS tab displays a checkmark
in the appropriate alarm/flag checkbox.
The second section of the MFC/MFS software tab is the
SPI Status Byte. This byte register contains control
bits and two read-only status bits. Unlike the other con-
trol and status registers, it is not memory mapped and
can only be updated through SPI instructions. It holds
several bits that control an elaborate scheme to prevent
inadvertent changes of data stored in the device.
Complete details of this scheme can be found in the
DS28DG02’s data sheet in the
Principles of Operation
section. See Table 3 for a listing of the SPI Status Byte
settings. To read these status/control bits, click on the
Read button. There are two ways to write to the regis-
ter. The first is to click on the checkboxes by the
desired settings to be activated. Placing a checkmark
in the boxes enables/activates the setting. This is
equivalent to adding a 1 in the bit field. Unchecking the
boxes deactivates/disables the settings. This is equiva-
lent to adding a 0 in the bit field. Any mouse click on a
checkbox writes immediately to the part. The second
method of writing entails calculating the byte value in
hex of the register. See the BITS column of Table 3 for
which bit position goes with which setting. After calcu-
lating the byte value, input the resulting hex number
into the Status text box and click the Write button.
Evaluates: DS28DG02
_______________________________________________________________________________________ 9
Table 2. Status Register Alarms and Status Flags
ALARM/FLAG BITS DEFINITION
RSTF: Reset Flag b0 RSTZ pin activity indicator; set whenever there is a pulse at RSTZ.
VCC ramp up: 1; VBAT attach: 0
WDA: Watchdog Alarm b1
Watchdog alarm indicator; set whenever the watchdog is enabled and the watchdog
timer expires.
VCC ramp up: 0; VBAT attach: 0
CLKA: Clock Alarm b2
RTC/calendar alarm indicator; set whenever the clock alarm is enabled and RTC and
RTC alarm register match.
VCC ramp up: 0; VBAT attach: 0
BORF: Battery-On Reset
Flag b3 Battery attach indicator; set whenever the voltage at VBAT ramps up above VBATmin.
VCC ramp up: not affected; VBAT attach: 1
PORF: Power-On Reset
Flag b4 Power-on reset indicator; set whenever the voltage at VCC ramps up above VCCmin.
VCC ramp up: 1; VBAT attach: 0
WPZV: Hardware Write-Protect
Value b5 WPZ pin state readout; reports the logic state at the WPZ pin.
VCC ramp up: WPZ pin state; VBAT attach: not affected
BATA: Battery Alarm b6
Low battery indicator; set whenever the battery alarm is enabled and if, during a
battery test, VBAT is below the selected VBAT trip point.
VCC ramp up: battery test if BME = 1; VBAT attach: 0
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
10 ______________________________________________________________________________________
Table 3. SPI Status Register
SETTING BITS DEFINITION
RDYZ: Ready
(Read-Only Bit) b0
Indicates whether an EEPROM write cycle is in progress.
check: write cycle in progress
uncheck: ready (normal state)
WEN: Write Enabled
(Read-Only Bit) b1
Indicates whether the device accepts a WRITE instruction; set through the WREN
instruction; cleared through the WRDI instruction or completion of a valid WRITE or a
valid WRSR instruction. Refer to the data sheet for definitions of WREN, WRDI, and
WRSR.
check: write enabled (power-on default)
uncheck: write enabled
BP[1:0]: Block Write
Protect b[3:2]
These bits specify which of the four user-memory blocks are write protected
(independent of WPEN and WPZ). Here 1 means checked and 0 means unchecked.
Settings:
00b not protected (factory default)
01b block 3 (0C0h to 0FFh) protected
10b blocks 2 and 3 (080h to 0FFh) protected
11b blocks 0 to 3 (000h to 0FFh) protected
WD[1:0]: Watchdog
Timeout b[5:4]
These bits specify the duration of the watchdog timeout if the watchdog is enabled
(WDE at address 134h = 1).
Settings:
00b 1.64s (factory default)
01b 820ms
10b 410ms
11b 200ms
These are nominal values. For tolerances, refer to the Electrical Characteristics in
the DS28DG02 data sheet.
RPROT: Register
Protection b6
Specifies whether the writeable addresses in the range of 120h and higher are write
protected (independent of WPEN and WPZ).
check: protected
uncheck: not protected (factory default)
WPEN: Hardware Write-
Protect Enable b7
Specifies whether b7:b2 of the SPI status register (nonvolatile bits) are writeable or
whether the WPZ pin state controls the write protection.
check: protection controlled by WPZ pin state
If WPEN = 1 and WPZ pin state is 0 the SPI status register is write protected and a
WRSR instruction is not valid.
uncheck: writable (factory default)
DS28DG02 Evaluation Board/Evaluation System
GPIO
Figure 7 shows the GPIO tab. Note that it consists of
four sections, each containing 12 checkboxes correlat-
ing to the 12 PIO pins of the DS28DG02. The EV board
was designed so that the first eight pins are input pins.
An 8-switch DIP switch block is provided to allow
changing the input states from 0 to 1 or vice versa. If
the user toggles a switch, clicking the Read All button
on the GPIO software tab shows the change.
Conversely, the last four pins (pins 8–11) of the EV
board were designed to be used as outputs. Each out-
put is associated with a green LED that responds to
changes of state of the output pin. The last four pins
can be switched on through software interaction,
specifically by clicking on the checkboxes labeled 8, 9,
10, and 11. The results show up on the EV board as
LEDs being turned on or off. Under Output Value,
Figure 7 shows the first eight pins in the off or logic 0
state. For the EV board it does not matter that these
checkboxes are on or off because the board uses the
pins as inputs, so output values are meaningless in this
situation. For more information about the DS28DG02’s
PIO schematic, see Figure 10. Conversely, the last four
pins under Output Value of the GPIO tab are checked
and are configured on the EV board as outputs. A
green LED lights when the output of one of the last four
pins is a logic 0. So, the checkmarks in Figure 7 would
indicate the LEDs are not lit. Unchecking them would
light the LEDs.
The second section of the GPIO tab is labeled
Direction. Each pin can be either an input pin or an out-
put pin. A checkmark (logic 1) by the pin number indi-
cates the pin is configured as an input. Unchecking the
pin configures it as an output. Figure 7 shows the first
eight pins configured as input and the rest as output.
The Inversion Mask is the third section of the GPIO
tab. When a pin is checked under this section, the
inverse of the state of the pin displays in the Input
Value section. It does not affect the actual state of the
pin, just the read-out.
Finally, the Input Value is the fourth section of the
GPIO tab. It shows the state of the pin with inversion
mask (if any) applied. Note that this is read-only and
the checkboxes cannot be changed.
Note that all four sections contain checkboxes indicating
each PIO pin by number. To write to each section’s reg-
ister, simply click on the checkbox by the pin number.
This action toggles the value and write the change to the
part immediately. There is also an alternate way to write
to the PIO registers. On the GPIO tab, three of the four
sections corresponding to the appropriate register have
Evaluates: DS28DG02
______________________________________________________________________________________ 11
Figure 7. DS28DG02 Evaluation Software: GPIO Tab
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
a text box located above the pin checkboxes. The text
box is editable with a Write button underneath. This
allows the user to calculate the desired PIO settings on a
bit level, and input the resulting hex number to the text
box. Click the Write button and the specific PIO register
changes accordingly.
The GPIO software tab contains two buttons to save
and restore default PIO settings. One way to experi-
ment with this is to set the DS28DG02’s PIO pins to the
desired states and/or settings and click the Save As
Default button. This saves the settings to the
DS28DG02. Next, change the settings and click the
Reload Defaults button. This restores the previous PIO
settings.
RTC
See Figure 8 for a screenshot of the RTC tab. This tab
allows for exercising and configuring the DS28DG02’s
RTC. It presents two sections. The top section is
labeled Real-Time Clock and contains text boxes to
input the time, date, and 24-hour time settings. Three
buttons are also located in this section. The Read RTC
and Write RTC buttons read the RTC, displaying the
time/date in the appropriate text boxes, or write what
has been entered into the text boxes to the
DS28DG02’s RTC. The third button is labeled Sync
RTC to PC, and when clicked, reads the PC’s clock
and writes the resulting time/date info to the
DS28DG02’s time registers.
The bottom section of the RTC tab is labeled RTC
Alarm. This section contains two buttons, one for read-
ing the alarm and one for writing the alarm. The alarm
settings can either be input or read into the text boxes
located in this section. The text boxes include the alarm
occurrence frequency (every second, minute, hour, day,
week, or month). They also allow the user to input the
time, date, or day associated with the alarm. When the
clock alarms, the red ALMZ LED lights on the EV board.
Note that the RTC and the RTC alarm must be enabled
prior to experimenting with the RTC tab. Enabling and
disabling the RTC and RTC alarm and clearing any
resulting alarm conditions are done on the MFC/MFS
software tab. To enable the RTC, check the box labeled
OSCE (oscillator enable). To enable the RTC alarm,
check the box labeled CAE (clock alarm enable). To
clear any resulting alarm condition that lights the red
ALMZ LED, click the Clear MFS button. The red ALMZ
LED then turns off.
12 ______________________________________________________________________________________
Figure 8. DS28DG02 Evaluation Software: RTC Tab
DS28DG02 Evaluation Board/Evaluation System
WatchDog
The WatchDog tab of the EV software provides a way
to exercise the DS28DG02’s watchdog. This tab simply
provides the option to select the watchdog input (WDI)
pin’s input frequency. The software provides the watch-
dog signal’s frequency to the WDI pin based upon the
user input on this tab. At least one input is outside any
of the watchdog timeout settings.
Additional setup of the DS28DG02 is required prior to
experimenting with the watchdog feature of the
DS28DG02. First, the user must enable some options
located on the MFC/MFS software tab. Specifically, the
user must check the oscillator enable (OSCE) and
watchdog enable (WDE) checkboxes. These settings
are part of the control register. Optionally, select the
desired output pin for the watchdog alarm. It can alarm
on either the WDOZ pin or the ALMZ pin. When alarm-
ing, either pin lights up the appropriate LED on the EV
board. The last items to set up for watchdog functionali-
ty are the WD1 and WD0 checkboxes under the SPI
Status Byte section of the MFC/MFS software tab.
These specify the duration of the watchdog timeout. See
Table 4 for the watchdog timeout settings. Note that the
WDI pin of the DS28DG02 can be floating when the EV
board is first connected to the CMAXQUSB command
module. Either grounding this pin or selecting the
WatchDog tab of the software and starting the watch-
dog signal on this pin defines the state of the pin and
allows further experimentation.
Detailed Description of
Hardware
Figure 9 is a visual overview of the hardware sections
of the DS28DG02 EV board. Many of the components
and their use are described in previous sections of this
document, so this section describes the components
not previously mentioned.
VBAT Monitoring
A battery can be connected to the DS28DG02 that sup-
plies power to the RTC and associated registers if VCC
is switched off. Because of this, the DS28DG02 was
designed with a built-in battery monitor. If the battery
voltage falls below a user-selected trip point monitored
on the VBAT pin, the DS28DG02 outputs an alarm. On
the EV board, the alarm lights up the red ALMZ LED.
To exercise the battery monitor on the EV board, first
place a jumper on the correct pins of J3. Jumper J3
allows the user to choose how the VBAT pin of the
DS28DG02 receives power, either through the on-
board battery or through VCC (powered by the PC’s
USB port). Place the jumper on the side of J3 labeled
VCC (leaving the jumper on BATT would prematurely
deplete the battery). Once that has been done, use the
software described in the
Detailed Description of
Software
section to enable the clock oscillator. Click on
the MFC/MFS tab and check the oscillator enable
(OSCE) checkbox. The battery monitor enable (BME)
checkbox should be checked along with selecting a
battery trip point (BTRP). See Figure 6 for the BTRP
selections, which are 1.75V, 2.00V, 2.25V, and 2.50V.
Just select the desired setting by clicking on it. Finally,
adjust the potentiometer R5 to a low value and rewind
the RTC to a few seconds before hour rollover as the
battery monitor tests the VBAT voltage every hour on
the hour. The RTC can be set on the EV board through
the RTC software tab. See Figure 8 for a screenshot.
The alarm shows on the EV board by lighting the red
ALMZ LED. It shows on the MFC/MFS software tab as
well. Click the Read MFC/MFS button, and the battery
alarm (BATA) checkbox is checked. To clear the
alarm, click the Clear MFS button. This switches off the
ALMZ LED.
Evaluates: DS28DG02
______________________________________________________________________________________ 13
Table 4. Watchdog Timeout Settings
Note: These are nominal timeout values. Check the DS28DG02
data sheet’s Electrical Characteristics table for complete
ranges.
WD1 WD0 TIMEOUT (ms)
Unchecked Unchecked 1600
Unchecked Checked 800
Checked Unchecked 400
Checked Checked 200
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
14 ______________________________________________________________________________________
Figure 9. DS28DG02 EV Board Component Map
• GROUND TEST POINTS (TP1 AND TP2)
• ALMZ AND WDOZ PINS (RED LEDs)
• PIO 8–11 GREEN OUTPUT INDICATOR LEDs
• RSTZ PIN (RED LED)
• J1 RESET-ENABLE JUMPER
• J4 WPZ WRITE-PROTECT PIN JUMPER
• R2 VCC INPUT POTENTIOMETER
• SW1 RESET BUTTON
• B1 3V LITHIUM CELL
• R5 VBAT INPUT POTENTIOMETER
• J3 VBAT SOURCE JUMPER
(CHOOSE BETWEEN BATTERY AND VCC)
• GPIO EXPERIMENTER'S HEADER
• GPIO INPUT DIP SWITCH
• DS28DG02
• 32kHz CRYSTAL
DS28DG02 Evaluation Board/Evaluation System
Reset Monitoring (VCC Monitoring and
Pushbutton Reset)
The reset monitor of the DS28DG02 generates a reset to
the CPU if the voltage at the VCC pin falls below the fac-
tory-set limit, which is between 2.97V and 3.14V with the
typical trip point falling at 3.05V. The reset output
includes a debounce circuit for manual pushbutton reset.
There are two methods to test reset monitoring of the
DS28DG02. The first is to simply push the reset push-
button switch labeled as SW1 on the EV board. Doing
so briefly lights the EV board’s red RSTZ LED; this is
also indicated on the MFC/MFS software tab of the EV
software by a checkmark in the reset flag (RSTF)
checkbox. To see the flag, the MFC/MFS screen must
be refreshed by clicking on the Read MFC/MFS button.
To clear the flag, click on the Clear MFS button.
The second method is by adjusting the R2 potentiome-
ter on the EV board until the red RSTZ LED lights up. To
do this, use a Phillips-head screwdriver and turn the
potentiometer counterclockwise. Next, refresh the
MFC/MFS software tab by clicking on the Read
MFC/MFS button. A check should appear in the RSTF
checkbox showing that the low voltage condition
occurred. To clear the flag, turn the potentiometer
clockwise until the light turns off and click on the Clear
MFS button on the MFC/MFS software tab.
Write Protection
The DS28DG02 provides robust write protection for dif-
ferent sections of on-board memory. The first section of
memory that has a write-protection scheme is the user
EEPROM area. This area consists of four separate
memory blocks of 64 bytes each. These can be write
protected through the EV software’s MFC/MFS tab
specifically by clicking on the BP0 and BP1 check-
boxes under the SPI Status Byte section. See Table 5
for the possible combinations of write protection avail-
able for user EEPROM block write protection.
The second section of memory with a write-protection
scheme is the block of memory addresses at 120h and
higher. This block is protected through the register pro-
tection (RPROT) bit of the SPI Status Byte. This bit can
be changed through software by clicking the RPROT
checkbox on the EV software’s MFC/MFS tab. A check-
mark indicates that the addresses are write protected;
no checkmark means that the addresses are writable.
The RPROT checkbox write protects the MFS, MFC,
and PIO registers. A valid experiment would be to
place a checkmark in the RPROT checkbox, and try to
read or write any of the registers that RPROT write pro-
tects. The attempts should be unsuccessful.
Finally, the previously mentioned SPI Status Byte can
be write protected. This is slightly more difficult to do
since the bit to write protect the SPI Status Byte is actu-
ally a part of the SPI Status Byte. This was intentionally
designed this way, as the SPI Status Byte is where all
write-protection settings are located. The bit to set is
the write-protect enable (WPEN) bit. On the MFC/MFS
software tab, click the checkbox labeled WPEN to turn
on write protection of the SPI Status Byte. Turning off
write protection of the SPI Status Byte requires the WPZ
pin of the DS28DG02 to be at a logic 1 state. When the
WPZ pin is at the logic 1 state, the SPI Status Byte is
writable even if WPEN is checked. Placing a jumper on
the rightmost two pins of J4 of the EV board can set the
WPZ pin to a logic 1, making an otherwise write-pro-
tected SPI Status Byte writable.
Evaluates: DS28DG02
______________________________________________________________________________________ 15
Table 5. User EEPROM Write Protection
with BP1 and BP0
BP1 BP0 PROTECTED MEMORY
0 0 Not protected (factory default)
0 1 Block 3 (0C0h to 0FFh) protected
1 0 Blocks 2 and 3 (080h to 0FFh) protected
1 1 Blocks 0 to 3 (000h to 0FFh) protected
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
16 ______________________________________________________________________________________
R2
100ΩVCC
R6
250Ω
R1
500Ω
C1
0.1μF
C2
0.1μF
R5
500Ω
VCC
VBAT CHIP
VCC CHIP
VCC CHIP
VCC
SB1
SW DIP-8
VCC
VBAT CHIP
TP1
GND
VCC CHIP
TP
TP1
GND
TP
1
2
B1
BATTERY BATTERY J3
BATT SRC
VCCLOAD
2
GND GND
J2
TO CMAXQUSB
4
6
8
10
12
14
1
3
5
7
9
11
13
2
J1
RESET LED ENABLE
SW1
RESET
1
GND
VCC VCC
GND
16
18
20
15
17
19
22
24
21
23
26
28
30
25
27
29
ALMZ WPZ
WDOZ
32
34
31
33
WDI
RSTZ
36
38
40
35
37
39
CSZ
SOS1
SCK
1
J6
PIO HEADER
2
3
PIO10
PIO11
PIO9
PIO8
PIO6
PIO7 4
5
6
7
8
9
PIO4
PIO5
PIO3
PIO2
PIO0
PIO1 10
11
12
1
J4
WPZ INPUT
2
3
WPZ
RP3
470Ω
D6
ALMZ
ALMZ
R8
10kΩ
D1
WDOZ
WDOZ
R9
10kΩ
D2
PIO11
PIO11
D3
PIO10
PIO10
D4
PIO9
PIO9
D5
PIO8
PIO8
D1
RSTZ
RSTZ
R3
10kΩ
RP2
100kΩ
RP1
1kΩ
X1
RSTZ DS28DG02
U1
1X1
X2
2
WDI
X2
32kHz VBAT CHIP
SCK
SI
CSZ
3RSTZ
4WDI
WDOZ
PIO0
5WDOZ
WPZ
6
PIO4
WPZ
7PIO0
8PIO4
PIO8
PIO10
9PIO8
GND
10
PIO6
11 PIO10
12 PIO6
PIO2 13 PIO2
VCC
14
28
VBAT
CSZ
SI
27
26
SCK 25
SO
PIO1
PIO5
ALMZ
24
SO
ALMZ
PIO5
23
22
PIO1 21
PIO9
PIO11
PIO7
20
PIO9
1
2
PIO7
PIO5
PIO4
PIO6
3
4
5
6
7
8
16
15
14
13
PIO3
PIO1
PIO0
PIO2
12
11
10
9
GND
PIO7
19
18
PIO11 17
PIO316
PIO3
VCC 15
R7
470Ω
Figure 10. DS28DG02 EV Board Schematics
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
______________________________________________________________________________________ 17
Figure 11. DS28DG02 EV Board Layout Top
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
18 ______________________________________________________________________________________
Figure 12. DS28DG02 EV Board Layout Bottom
DS28DG02 Evaluation Board/Evaluation System
Evaluates: DS28DG02
______________________________________________________________________________________ 19
Figure 13. DS28DG02 EV Board Layout Composite
DS28DG02 Evaluation Board/Evaluation System
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
20
________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Evaluates: DS28DG02
DS28DG02 Evaluation Board/Evaluation System
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 7/07 Initial release. —
1 5/08
Removed technical support ticketing system link from the Support Resources
section and replaced with the company technical support web address. 1
