20C12 HART MODEM Introduction HART is a trade mark of Rosemount Corpora- tion. The NCR 20C12 (Highway Addressable Re- mote Transducer) HART low power FSK modem is a single chip CMOS model that operates at the Bell 202 standards. The NCR 20C12 HART modem is ideally suited for factory automation, especially in areas that re- quire ultra low power such as intrinsically safe environ- ments. Features * Operates at the Bell 202 Standard Forward Bit Rate of 1200 bits/sec Uses the Bell 202 Shift Frequencies of 1200 Hz and 2200 Hz Transmit Modulation of 1200 Baud Receive Modulation of 1200 Baud * Single Chip Frequency -Shift-Keying (FSK) Optimal for Intrinsically Safe Applications Singel 5-V Power Supply * CMOS and TTL Compatible Reliable CMOS Technology 16 pin DIP or 28-pin PLCC packages available NCR Communications Products 04/88 General Description The NCR 20C12 (Highway Addressable Re- mote Transducer) HART low power FSK Modem is a single-chip, CMOS modem for use in process control in- struments or other low power equipment. The modem circuitry is digital. It provides only the modulating and demodulating functions and is intended to be used with external circuits which may amplify, filter, and shape the media signals. The modem operates at the Bell-202 standard upper (forward) bit rate of 1200 bits/sec and uses the Bell-202 shaft frequencies of nominally 1200 Hz and 2200 Hz. With proper conditioning of them media, it can communicate with other Bell-202 modems. To conserve power, the demodulator is stopped while the modulator operates and vice versa. Therefore, operation is half-duplex. The modem is packaged in a standard 16-pin Dual In-line Package (DIP) or in a 28- pin Plastic Leaded Chip Carrier (PLCC). The HART modem operates from a single 5-volt supply and requires an externally generated clock fo 460.8 kHz. The modem provides an active low carrier de- tect output and a 19.2 kHz clock output. No external ad- justments or special biasing are required. 305 ie] 2 = ed 5 a) ea za nn) as a = ro] aPin Description INPUT PIN # or SIGNAL |ouTPUuT DIP | PLCC DESCRIPTION VDO . 1 1 + & V power supply O19_2k [e) 2 2 User clock. Nominally 19.2 kHz (16 times bit rate). co o 3 3 | Carrier Detect is low (0) when carrier ts present. IRXA ! 4 4 Demodulator Input accapte 1200 (2200) Hz square wave FSK modulated carrlar, NC . 5 -12|No internal connection. ITEST1 i 8 13 | Test Inout One must be connected to VSS during normal operation. NC . 7 - | No Internal Connection, ORXD 0 8 14 |Demodulater Output provides a logic f (0) in rasponse to a 1200 (2200) Hz FSK square wave signal at IRXA. Demodulation takes place only whan INRTS is a high (1). With INRTS low (0) the ORXD output is not defined. Vss - 9 18 |Power supply ground. NG > 16 - No Internal connection. OTXA oO 11 16 | Modulator Output provides a equare wave FSK output 1200 (2200) Hz in response to a@ logic 1 (0) applied to ITXD, OTXA Ig active when INATS Is low (0). It goes to a high-impedance state when INRTS Is high (1). INRTS { 12 17 | Request To Send selects operation of the modulator when low (0) and the demodulator when high (1), causing OTXA to go to a high-impedance state when high (1). ITESTO I 13 26 = | Test Input Zero must be connected to VSS during normal operation. ITXD ! 14 27 |Modulator input accepts Input data {logic 1 or 0) for modulating the carrier output at OTXA. NG a 16 {18-25 [No Internal Connection. {460K | 16 2g | input Clock clocks the modem circultry; the frequency ig nominally 460.8 kHz. Note: Slgnal names starting with 'l are inputs and signal names starting with O' are outputs. 306 NCR Communications Products 04/88Pin Out 16 Pin Dip 28 Pin PLCC x x $ as ah a egses ce VOD oy 7 16 b I1460K AoOO AMA O19_2K co 16 bp NG 4 3 2 1 28 27 26 OCD qs 14 6 ITXD nc Cs 25 [INC IAXA 54 13 by ITESTO No C6 24 FING NC ds 12 by INATS No C7 NcR 7 =e ITEST1 ces 14 fy OTXA nc [8 22 NC G7 10 2 NC NC EJs ORXD js oki vss NC Cj 10 20 [INC NG C11 io CNG 12 13.14 18 18 17 18 OU UU OU 2588 28 Electrical Characteristics The conditions for the following electrical characteristics apply to the full operating temperature range with a supply voltage of 5.0 volts. wn Pa a) Loni to i) pe m9 i=] sc a a lon o DC Characteristics Absolute Maximum Ratings SYMBOL PARAMETER MIN MAX UNIT TSTG Storage Temperature -65 160 c TA Operating Free-air -40 +85 C Temperature VOD Supply Voltage (non-operating) 7 Vv Cautions 1. CMOS Devices are damaged by high energy electrostatic discharge. Devices must be stored in con- ductive foam or with all pins shunted. Precautions should be taken to avoid application of voltages higher than the maximum rating. 2. Remove power before insertion or removal of this device. 3. Stresses above absolute maximum ratings may result in damage to the device. Functional opera- tion of devices at the absolute maximum ratings or above the recommended operation conditions specified in this document is not implied. NCR Communications Products 04/88 307Operating Conditions SYMBOL $$PARAMETER MIM = MAX) =s UNIT CONDITIONS voo Supply Voltage Vv VIN Input Voltage VSS -0.3 VDD +0.3 Vv VIH Logical 1 input Voltage V VIL Logical 0 input Voltage Vv VOL Output Low Voltage Vo Qutput Sink Current=4.0mA VOH Output High Voltage V Output Source Current=4.0mA {DD* Supply Current pA During Demodulation pA Burling Modulation lIN input Leakage Current HA VIN=VDD or VSS ITS High-Impadance Output +/- 10 pA typical Applies only to OTXA Leakage Current CIN Input Capacitance 308 (DD NOTES: * SOpF load on all outputs * All Input rise and fall time requirements satisfied + Glock (/460K) freqe460.8kHz +/-0.1% See the following Current ve Voltage Charts for more information. NCR Communications Products 04/88Current vs Voltage Charts Modulation MicroAmps 110 100 a | I I T st Power Supply Voltage Demodulation mani 101010N BN) MicroAmps Zz J ca L Zz D es = co) oO 480 460 440 420 400 Power Supply Voltage NCR Communications Products 04/88 309AC Characteristics Clock Pulse Widths: Clock Rise and Fall Time: IRXA Input Rise and Fall Time: Other Inputs Rige and Fall Time: Output Rise and Fall Time*: Clock Frequency (at the I1460K pin): 460.8 kHz +/- 0.1% high level = 150 nanoseconds min. low level = 150 nanoseconds min. 10 nanoseconds max. 200 nanoseconds max. 50 nanoseconds max. 10 nanoseconds max. *Condition: 50 pF capacitance on ali outputs. Modem Characteristics Carrier Detect Carrlar Detect Frequency Range: This Is the range of frequencies applied at IRXA over which OCD must ge low {logic 0). Conditions: 1) Clock (II460K) frequency of 460.8 kHz +/- 0.1%. 2) Input (IRXA) asymmetry of 5% max. 1000 Hz to 2575 Hz. Time From Carrier Input To Carrier Detect: This fs the time from the start of a valld carrier signal at IRXA until OCD goes to logle low (0), Minimum = 9.0 millisec. Maximum = 15.0 millisec. Time From Carrier Loss To Garrlar Undetect: This Is the tlme from the loss of a valid carrler signal at IRXA until OCD goes to a logic high (1). 1 millisecond maximum User Clock (019_2K) Frequency: This clock frequency is proportional to the 460.8kHz clock at 460K. 19.2 kHz nominal. NCR Communications Products 04/88Modulator Modulator Output Frequency (at the OTXA pin): Nominal high frequency (logic 0 applied to ITXD) = 2194.3 Hz Nominal lew frequency (logic 1 appiled to ITXD) 1196.9 Hz ne oe eit cutput frequencies are proportional to the Input clock frequency (applied to the 46 pin). Modulator phase continuity error: +/- 10 degrees maximum. Demodulator Maximum Demodulater Jitter: +/- 12% of one bit time Conditions: 1) Input frequencies at 1200 Hz +/- 10 Hz and 2200 Hz +/- 20 Hz. 2} Clock (Il460K) frequency of 460.8 kHz +/- 0.1 %. 3) Input (IRXA) asymmetry = 0. Representation of Jitter: began tl/-12% ag) ORXD ie) S 4 = i NOMINAL TRANSITION TIME ZS =a S oO NCR Communications Products 04/88 311Functional Description The modem uses shift frequencies of nominally 1200 Hz (representing a digital one) and 2200 Hz (dig- ital zero). The bit rate is nominally 1200 bit/second. There are four major functional blocks: clocks, demodu- lator, modulator and carrier detect. Clocks The clock section accepts a digital input fre- quency of 460.8 kHz from an external source. This is used in various counter arrangements to generate several internal clocks. One internal clock at a nominal fre- quency of 19.2 kHz is also brought to an output pin for use in reconstructing the data in circuits external to the modem. All circuit operations can be performed with a master clock frequency of 460.8 kHz. This is considera- bly lower than the clock frequencies used in existing single-chip modems and contributes to a low current consumption. Various sections of the model are shut down (not clocked) when not being used. This further reduces power consumption. Demodulator The demodulator accepts an FSK signal at its IRXA input and reproduces the original modulating sig- nal at its ORXD output. Both the input and output are digital signals as illustrated below. A simplified modulator block diagram is shown below. It works by counting down one or the other of two clocks, A or B, depending on whether the input sig- nal is high or low. Clock A (153.6 kHz) is derived by di- viding the 460.8 kHz oscillator frequency by 3. Clock B (83.78) kHz is derived by dividing the 460.8 kHz oscil- lator frequency by 5.5. The counter in the diagram is a divide-by-70. This means that the two shift frequencies are 1196.9 Hz and 2194.3 Hz. Since the modulator works by counting down clocks, its output transitions are quantized as to when they can occur. The maximum timing error due to quan- tization is 12 microseconds, which is the period of the slower of the two clocks, A and B. At the higher of the two shift frequencies (2200 Hz), the phase error is 9.5 degrees, and at the lower of the two shift frequencies the phase error is 5.2 degrees. excel 183.6kHz - +70 Counter TXA 83.8kHz ot Modulator Block Diagram Carrier Detect The active low carrier detect works by looking for incoming signal frequencies in the approximate range of 1200 Hz to 2200 Hz. This is done by measuring SUL ee interval times between input transitions. If several suc- __J- 4 cessive interval time measurements fall within specific 0 1 1 a 1 DATA limits, carrier detect is indicated, and the carrier detect 11200 SEC ed output is asserted. If, after the carrier has been detected, the measured interval time falls outside of these limits for some length of time, the carrier detect output is unas- serted. Demodulator Signals Modulator The modulator accepts digital data in NRZ form at its ITXD input and generates the FSK modulated signal at its OTXA output. An additional requirement for the modulator is that it provide phase continuous modulation. That is, when switching from one to the other of the shift frequencies, the phase angle of the modulated signal is preserved. 312 NCR Communications Products 04/88Typical Application The modem will usually be applied as shown in the block diagram below. The received signal is filtered to reduce noise. The filter should include the band of fre- quencies from about 900 Hz to 2.5 kHz. The output of the filter is applied to the input of a comparator to pro- vide the required signalling levels to the modem. Addi- tional amplification may be required ahead of the filter to provide sufficient signal to the comparator. Be sure that the comparator switches at the zero crossings of the incoming waveform and is glitch free. Depending on the application, the output filter may not be necessary. Omitting it will cause square waves to be applied to the signalling media. A schematic showing a typical applications fol- lows the block diagram. COMPARATOR BANDPASS rl FILTER IRXA AT CREAE 480K OSCILLATOR FILTER OTXA HART MODEM MICRO. Pt | __ ed INATS COMPUTER pa oco RXD }-_] oF ITXD Block Diagram of a Typical Application HART MODEM ZERO CROSSING 5 VDD li460K BANOPASS FILTER OETECTOR qdmoie 2k NCE iL ooo ITXD FI 1 + > IAXA ITESTO = 001 2uF iy na] .0012uF my NC INRTS A | 26.1K COMPARATOR np | a A > SjITESTt OTXAR VDOv2. + | |! OP AMP ; clonn ves i" AA, A 500K Schematic of a Typical Application NCR Communications Products 04/88 313 ie] Fa 2a weed eae os a] =e = a = S ca)Mechanical Drawings 16-Pin Dual In-line Package (DIP) Note: All units are 1/1000 inches 750 ow" " HO 0 280 q UuUoguUUuU uu wowed Lo le aw | mm oe rT au pe 350 314 NCR Communications Products +/+40 04/8828-Pin Plastic Leaded Chip Carrier (PLCC) Package Note: All units are 1/1000 inches 7(8X) 30 35 | \ 15 \\ PIN 4 60 rrP 225 DETAI OE pe X: SURFACE MOUNT POINT 910420 10227 re) 2 2 Leal be ae) i) as) 2 oa = for) o 60210 ; q ae \ Hl o I \ ye SEATING lirss + PLANE 16 MIN M3226 om SIDE VIEW BOTTOM VIEW NCR Communications Products 04/88 315