AMD Am79191 WORLD CHIP FSK AUTODIAL MODEM Data Sheet
Contents
1. RESET MODES 18 23 30 32 32 43 44 45 PRELIMINARY AM79101 DATA SHEET ABSOLUTE MAXIMUM RATINGS DC CHARACTERISTICS SWITCHING CHARACTERISTICS PERFORMANCE m APPLICATIONS 4 PHYSICAL DIMENSIONS 4 4 PRELIMINARY AM79101 DATA SHEET Table of Figures Block Diagram s acc 6 Connection Diagrams 7 Figure 1 Loopback Configurations 18 Figure 2 Transmitter Block Diagram 20 Figure 3 Receiver Block Diagram us e Mar Se Jer de 20 Figure 4 Full Duplex Channel Assignments lt I 22 Figure 5 Half Duplex Channel Assignments ai en 22 Figure 6a Autodial Flowchart EE 62 26 Figure 6b Autodial Timings 28 lar SOE 265 27 Figure 7 Autoanswer Flowchart 28 Figure 7b Autoanswer Timings essa e eee 29 Figure 8a Transmit Main Channel State Diagram oe 34 Figure 8b Transmit Back Channel State Diagram 352. aoa 859 083 GEORGIA 404 449 7920 ILLINOIS CHICAGO cores d or 312 773 4422 emi ee ed eee v ote vid ee sae 312 505 9517 ille INDIANA 317 244 7207 KANSAS eet sg Kon 451 3115 MARYLAND 1 814 275 4415 201 299 0002 315 457 5400 914 471 8180 Woodbury 518 364 8020 NORTH CAROLINA 919 847 8471 OHIO 614 891 6455 Columbus 614 891 6455 Dayton 503 439 0470 EGON 503 245 0080 PENNSYLVANIA Allentown 215 398 8006 215 657 3101 612 346 7830 i 214 934 9099 713 785 9001 206 455 3600 WISCONSIN 414 792 0590 ADVANCED MICRO DEVICES INTERNATIONAL SALES OFFICES BELGIUM KOREA Seoul nits 82 2 784 7598 Bruxelles TEL 02 771 91 42 FAX 82 2 784 8014 FAX 02 762 37 12 LATIN AMERICA 61028 Ft Lauderdale TEL uns og 484 8600 FRANGE FAX 305 485 9736 2 1 49 75 10 10 1 48 75 10 13 MOM EOS 263282 GERMANY Hannover area TEL 05143 50 55 FAX 05143 55 53 TLA 925287 M nchen TEL 089 41 14 0 JA 2246 FAX 08
3. BCD changes to LOW and valid data can be obtained at BRD Data is received until the receiver detects loss of back channel received signal for at least the time tgcporr At this time BCD goes HIGH BRD is clamped to a Mark if V 23 mode or 202 150 bps back channel mode is selected For 202 5 bps back channel mode BCD represents the received data BRD can be ignored The state machine returns to the idle loop at point E LOOPBACK Eleven modes exist to allow both analog and digital loopback for each modem specification met by the Am79101 When a loopback mode is selected the signal processing filters etc for both the transmitter and receiver is set to process All timing delays are listed in Table 5 32 PRELIMINARY AN79101 DATA SHEET the same channel or frequency band This allows the analog output TC and the analog input RC to be connectad externally for local analog loopback Alternately the digital data signals TD and RD or BTD and BRD can be connected externally allowing a remote modem to test the local modem with its digital data signals looped back When a loopback mode is selected the state machine sequences are altered slightly If a half duplex loopback mode is selected 202 or V 23 the local CD BCD is not forced HIGH when RTS BRTS is asserted 33 PRELIMINARY 3147 9 101 DATA SHEET AMT Ad He Figure 8a Transmit Main Channel State Diagram 34 PRELIMINARY AM79101 DATA SHE
4. After CTS changes to HIGH the state machine returns to point A in Figure 8a Half Duplex When a half duplex mode is selected 202 or V 23 data transmission can be either on the main channel at 1200 600 bps or on the back channel at 5 75 150 bps In normal half duplex operation a single modem is either transmitting on the main and receiving on the back channel or vice versa In the Am79101 control of the transmitter and receiver filters to the proper channel is performed by RTS When RTS is asserted the transmitter filters and synthesizer are set to transmit on the main channel the receiver filters are set to receive on the back channel Therefore whenever RTS is LOW BRTS should not be asserted since the transmitter cannot be used for the back channel When RTS is HIGH and a half duplex mode is selected the transmitter filters and synthesizer are set to the back channel the receiver filters are set to the main channel If RTS and BRTS are asserted simultaneously RTS will take precedence However if BRTS is asserted before RTS and the the back channel data transmission sequence has been entered Figure 8b RTS will be ignored until BRTS is set HIGH The state machine sequences for main and back channel transmission differ slightly and are depicted in Figures 8a and 8b Assume the state machine is idling through point in Figure 88 All timing delays are listed in Table 5 30 PRELIMINARY 147 9101 DATA SHEET Main
5. 0 652 VRMS 1 5 Vir Output Voltage Output Voltage 0 820 HIGH Group 0 5 Output Voltage 0 518 VAT Answer Tone 3 5 Modulated Transmit Output TC DC Offset Harmonics from Fundamental Frequency Accuracy Except 202 Frequency Accuracy 202 Mark Out of Band energy See Figure 19 49 PRELIMINARY AM79101 DATA SHEET SWITCHING CHARACTERISTICS Continued Receiver Input Description Min Typical Units RC Input Voltage Input Resistance Kohns FroL Frequency Deviation Tolerance 16 16 Carrier Detect On Level VeDOFF Carrier Detect Off Level Carrier Detect Call On Level 37 dBm VCDCOFF Carrler Detect Call Off Level 41 Bm Carrier Detect Hysteresis Note All TC Levels are measured using a 1200 ohm Load All dBm measurements are referenced to 600 ohm PERFORMANCE Figure 18 shows a graph of nominal bit error rates for the various modem types A flat line condition back to back wire connection is used to allow easy correlation by users 50 Bit Error Rate 4 Receive Level 30dBm 4 Gaussian Noise 4 Flat Line Room Temperatura Equalizer out Signal to Noise Ratio dB Figure 18 Am79101 Nominal Bit Error Rate 51 dB PRELIMINARY AM79101 DATA SHEET FREQUENCY kHz This is the Ouput Level Relative to the Transmitted Signal This Chart Applies to Frequencies Othe
6. 592 0090 THORSON DESERT STATES 505 293 8555 Mississauga Ontario NEW YORK LECTRONICS 418 676 9720 INC 315 437 8343 VITEL ELECTRONICS 514 636 5951 Columbus IDAHO DOLFUSS ROOT amp 614 885 4844 INTERMOUNTAIN TECH MKGT 208 888 6071 Dayton INDIANA DOLFUSS ROOT 8 CO 513 433 6776 SAI MARKETING CORP 317 253 1668 Strongsville IOWA DOLFUSS ROOT amp 216 238 0300 LORENZ 5 1 5 319 377 4656 PENNSYLVANIA KANSAS DOLFUSS ROOT amp 412 221 4420 LORENZ SALES 913 384 6556 UTAH R MARKETING 801 595 0631 Advanced Micro Devices reserves the right to make changes in its product without notice in order to improve design or performance characteristics The performance characteristics listed in this document are guaranteed by specific tests guard banding design and other practices common to the industry For specific testing details contact your local AMD sales representative The company ADVANCED MICRO DEVICES 901 Thompson Pi P O Box 3453 Sunnyvale 94088 USA TEL 408 732 2400 TWX 910 339 9280 TELEX 34 6306 e TOLL FREE 800 538 8450 APPLICATIONS HOTLINE TOLL FREE 800 222 9323 assumes no responsi
7. appear at the RECEIVED DATA RD pin A Carrier Detect signal CD is also digitally extracted from the received line carrier to indicate valid data In the Call Mode the MC inputs select the proper digital bandpass filters to detect answer tones or call progress tones at RC Presence of a valid tone will be indicated by CD The on chip hybrid provides the analog interface which communicates TC and RC directly over two wires to and from the telephone line via a DAA 19 PRELIMINARY AM79101 DATA SHEET MCo MC Figure 2 Transmitter Block Diagram FROM DAA ACOUSTIC COUPLER Figure 3 Receiver Block Diagram Interface Control This section controls the handshaking between the modem and the local terminal It consists primarily of delay generation counters two state machines for controlling transmission and reception and mode control decode logic Proper transmit frequencies and transmit receive filters are selected according to the specified modem type or function in the Data or Call Mode Inputs to and outputs from this section are as follows DATA CALL MCg MC DATA TERMINAL READY REQUEST TO SEND Main and Back CLEAR TO SEND Main and Back CARRIER DETECT Main and Back RESET 20 PRELIMINARY 79101 DATA SHEET Internal logic clamps the handshake signals to different levels under certain conditions e g initial conditions When Bell 103 113 and V 21 modem configurations are selected the bac
8. of power VBB 5 Volt Power Supply VCC 5 Volt Power Supply XTALa Non TTI Compatible Master timing of the modem is provided by either a crystal connected to these two pins or an external clock inserted into The value of the crystal or the external clock frequency must be 2 4576 MHz 01 14 PRELIMINARY AM79101 DATA SHEET Table la Mode Controls in the Data Mode DA CA HIGH a Bell 103 Originate 300 bps full duplex Bell 103 Answer 300 bps full duplex Bell 202 1200 bps half duplex with 5 bps back channel Bell 202 1200 bps with amplitude equalizer and 5 bps back channel CCITT V 21 Originate 300 bps full duplex CCITT V 21 Answer 300 bps full duplex CCITT V 23 Mode 2 1200 bps half duplex CCITT V 23 Mode 2 with amplitude equalizer 1200 bps half duplex CCITT V 23 Mode 1 600 bps half duplex Reserved Bell 202 1200 bps with 150 bps back channel Bell 202 1200 bps with amplitude equalizer and 150 bps back channel CCITT V 23 Mode 1 600 bps with soft turn off Reserved CCITT V 23 Mode 2 1200 bps with soft turn off CCITT V 23 Mode 2 1200 bps with amplitude equalizer and soft turn off P Up to 150 bps back channel is avallable Note Reserved modes should not be entered 15 PRELIMINARY AM79101 DATA SHEET Table la Mode Controls in the Data Mode DA CA HIGH Con
9. transfer can now begin Figures 6a and 6b show the Autodial flowchart and timings As a called modem the Am79101 will be placed in the Call Mode by the external microprocessor which receives a ring indication signal from the DAA Autoanswer begins by using Figures 7 and 7b show the Autoanswer flowchart and timings Call Progress Tone Detection CPTD The CPTD filter passes call progress tones from all the major Post Telephone and Telegraphs PTTs The cadences tenporal patterns of CD will identify the following signals Primary Dial Tone Secondary Dial Tone Ringback Signal Network Busy Signal Busy Signal Each country s PTT may have different requirements for the cadences of these call progress tones Dual Tone Multi Frequency DTMF Tone Generation The Am79101 transmitter can generate the basic 3 x 4 matrix as Shown in Table 4 According to the Bell specifications the minimum duration for the DTMF digit is 50 ms The minimum interdigit interval silence is 45 ms The minimum time from the beginning of one DIMF digit to the next is 100 ms It is common practice to extend the DTMF digit duration to insure detection by the central office Once in the Call Mode RTS controls the duration of the DTMF tone With DTR LOW and the desired digit applied to the MC pins setting RTS LOW will generate the DTMF tone at TC until 24 PRELIMINARY 7 57 9101 DATA SHEET RTS is set HIGH The user has complete control of th
10. with 5 bps Back Channel tp is an external delay provided by the user tp gt 0 This timing diagram is not to scale See Table 5 for values 39 PRELIMINARY AM79101 DATA SHEET E a BRTS n BACKDATA 4 E 411 LL gp Figure 11 CCITT V 23 Handshake Timing tp is an external delay provided by the user tp gt 5 ms This timing diagram is not to scale See Table 5 40 PRELIMINARY AM79101 DATA SHEET HL WIL poe e Ep Eg em e BET NEC ER ee fe 9 lo Figure 12 V 23 STO and Bell 202 150 bps Handshake Timing tp is an external delay provided by the users 0 This timing diagram is not to scale See Table 5 for values 41 PRELIMINARY AM79101 DATA SHEET Figure 13 Bell 103 V 21 Handshake Timing This timing diagram is not to scale See Table 5 for values 42 PRELIMINARY AM79101 DATA SHEET CLOCK GENERATION Master timing of the modem is provided by either a crystal connected to the XTAL and XTAL2 pins or an external clock applied to XTAL Crystal When a crystal is used it should be connected as shown in Figure 14a The crystal should be a parallel resonance type and its value must be 2 4576 MHz 01 A list of crystal suppliers is shown below External Clock This clock signal could be deri
11. 9 406490 RS55650 MMI RS 523883 Stuttgart TEL 0711 62 33 77 SWEDEN Stockholm TEL 8 733 03 50 FAX 0711 625187 FAX 08 733 22 85 721882 TEX SORTE EE 11602 HONG KONG Kowloon TEL 852 3 695377 TAIWAN TEX 886 2 7122066 FAX 852 123 4276 FAX une 886 2 7122017 TLX 504260AMDAPHX UNITED KINGDOM 5 Famborough 0252 517431 ITALY Milano TEL seven 09 0252 521041 2 3533241 TL cee eee ene 858051 FAX 02 3498000 Manchester area 0925 828008 TER 32 3152 0925 827693 JAPAN Te ees 628524 Tokyo TEL 03 345 8241 London area 04862 22121 FAX 03 342 5196 04862 22179 x J24064AMDTKOJ 859103 Osaka TEL 06 243 3250 FAX een 06 243 3253 NORTH AMERICAN REPRESENTATIVES CALIFORNIA MICHIGAN FANG 22 EE iere ET OEM 408 988 3400 SAI MARKETING CORP 313 750 1922 DIST 408 498 6868 MISSOURI CANADA LORENZ SALES 314 99 4558 Calgary Alberta NEBRASKA TEL ELECTRONICS 403 278 5833 LORENZ SALES 402 475 4660 Kanata Ontario NEW MEXICO VITEL ELECTRONICS 613
12. Am79101 WORLD CHIP FSK AUTODIAL MODEM Preliminary Data Sheet Publication amp Rey Amendment 09833 B 70 Issue Date September 1987 Am79101 PRELIMINARY DATA SHEET Am79101 FSK AUTODIAL MODEM PRELIMINARY DATA SHEET PRELIMINARY AM79101 DATA SHEET PRODUCT SPECIFICATION THE Am79101 FSK AUTODIAL MODEM PRELIMINARY DATA SHEET DECEMBER 1987 CONTENTS DISTINCTIVE CHARACTERISTICS GENERAL DESCRIPTION ORDERING INFORMATION PIN DESCRIPTION 4 4 Setup Controls Transmitter I O Receiver I O Miscellaneous FUNCTIONAL DESCRIPTION Transmitter Receiver Interface Control CALL ESTABLISHMENT Call Progress Tone Detection CPTD Dual Tone Multi Frequency DTMF Tone Generation Answer Tone Detection Answer Tone Generation DATA TRANSMISSION Full Duplex Half Duplex Main Channel Soft Turn Off Squelch Back Channel DATA RECEPTION Full Duplex Half Duplex LOOPBACK retten nee CLOCK GENERATION lt
13. Channel This transmission sequence is entered if a 202 or V 23 mode is selected and RTS is asserted Since the receiver is now forced to the back channel the RECEIVED DATA RD signal is clamped to a Mark and the CARRIER DETECT CD signal is clamped HIGH The TRANSMITTED DATA TD input is released and a carrier appears at the TRANSMITTED CARRIER TC output which follows the Mark Space applied to TD RTS going LOW initiates a delay trcon at the end of which the CLEAR TO SEND CTS output goes LOW When CTS goes LOW data may be transmitted through TD Data transm ssion continues until RTS is set HIGH At this time several events are initiated First a delay trcorF is initiated at the end of which CTS goes HIGH TD is ignored as soon as RTS goes HIGH If a 202 mode or V 23 soft turn off mode is selected a soft turn off tone appears at TC for a tine followed by silence 0 0 Volts For both 202 and V 23 modes squelch period tso is initiated when RTS goes HIGH During this period the CD output is clamped HIGH forcing the RD output to a Mark condition The squelch period begins as soon as RTS goes HIGH and thus overlaps both trcoFF and tgpo At the end of the squelch period the state machine returns to the idle loop at point A in Figure 8a The reasons for squelch and soft turn off are as follows Soft turn off When RTS goes HIGH at the end of a message transients occur which may cause spurious Space signals to be recei
14. ET Figure 8b Transmit Back Channel State Diagram 35 PRELIMINARY AM79101 DATA SHEET Receiver Main Back Channel State Diagram Figure 9 36 PRELIMINARY AM79101 DATA SHEET Table 5 Timing Parameters Refer to Figures 6b 10 11 12 and 13 for Timing Diagrams Bell Symbol Description 103 Request to Send to Clear to Send ON Delay Request to Send to Clear to Send OFF Carrier Detect ON Delay 2 106 300 312 CDOFF Carrier Detect OFF Delay 21 40 21 40 tcDCON Carrier Detect Call 5 ON Delay 92 106 tcpcorr Carrier Detect Call 6 OFF Delay 21 40 37 PRELIMINARY AM79101 DATA SHEET Table 5 Timing Parameters Continued Refer to Figures 6b 10 11 12 and 13 for Timing Diagrams CCITT Symbol Description v 23 Request to Send 1 to Clear to Send ON Delay tncorr Request to Send 2 to Clear to Send OFF Delay BRCON Back Channel 7 Request to Send to Clear to Send ON Delay tprcorr Back Channel 8 Request to Send OFF Delay tc Carrier Detect ON Delay tcporr Carrier Detect 4 OFF Delay Back Channel 9 Carrier Detect ON Delay tseporr Back Channel 1 Carrier Detect OFF Delay Squelch Duration Transmitter Soft Turn Off Duration For V 23 Soft Turn off modes only 38 PRELIMINARY AM79101 DATA SHEET ES a MEN 5 EN I 4 Figure 10 Bell 202 Handshake Timing
15. Figure 9 Receiver Main Back Channel State Diagra NN 36 Figure 10 Bell 202 5 bps Handshake Timing 44 39 Figure 11 V 23 Handshake Timing e o 40 Figure 12 CCITT V 23 STO amp Bell 202 150 bps Handshake Timing sale a e Siw ee 4 41 Figure 13 Bell 103 CCITT V 21 Handshake Timing 42 Figure 14a Clock Generation e 9 9 9 c 5 9 43 Figure 14b External Clock 2 2 on on n 44 Figure 15a Automatic Reset e 9 9 t 44 Figure 15b Reset Timing Diagrams 06 9 9 2 c 45 Figure 16 Mode Setup 45 Figure 17 Power Supply Connections s s s s 46 Figure 18 Nominal Bit Error Rate 51 Figure 19 Out of Band Transmitter Energy 52 Figure 20 300 bps Full Duplex Modem des wer w bros 53 Figure 21 1200 bps Half Duplex Modem s s 54 Figure 22 Data Access Arrangement iwl 55 Table la Mode Controls in the Data Mode DA CA HIGH 15 Table lb Mode Controls in the Call Mode DA CA LOW 17 Table 2 Initial Conditions es e s es 21 Table 3 Frequency Parameters s s 23 Table 4 DTMF Tone Combinations 29 Table 5 Timing Parameters 6 6 6 a 9 9 n 37 Table 6 Clocking Parameters ve ee es 44 copyright 1987 Advanced Micro Devices Inc Advanced
16. Micro Devices reserves the right to make changes in its products without notice in order to improve design or performance characteristics The performance characteristics listed in this data sheet are guaranteed by specific tests correlated testing guard banding design and other practices common to the industry For specific testing details contact your local AMD sales representative The company assumes no responsibility for the use of any circuits described herein 4 PRELIMINARY AM79101 DATA SHEET Am79101 FSK AUTODIAL MODEM WORLD CHIPIM DISTINCTIVE CHARACTERISTICS Bell 103 113 108 and CCITT V 21 compatible at 300 bps full duplex o Bell 202 and CCITT V 23 compatible at 1200 bps half duplex with up to 150 bps back channel CCITT V 23 modes with optional soft carrier turn off feature o Single chip digital signal processor Autodial support Dual Tone Multi Frequency DTMF Tone Generation Call Progress Tone Detection Answer Tone Detection o Integral 4 to 2 wire hybrid o Public Switched Telephone Network PSTN response times o Serial RS 232C CCITT V 24 type handshake interface and protocol PRELIMINARY AM79101 DATA SHEET GENERAL DESCRIPTION The Am79101 World Chip is a single chip asynchronous Frequency Shift Keying FSK modem that is compatible with the applicable Bell and CCITT recommended standards for 103 113 108 202 V 21 and V 23 type modems All modulation demodulation filtering analog to digit
17. PRELIMINARY AM79101 DATA SHEET SET RTS HIGH FOR BILLING DELAY SET RTS LOW FOR ANSWER TONE DURATION SET RTS HIGH FOR SECOND SILENCE DURATION SELECT MODEM MODE ENTER DATA MODE BEGIN DATA TRANSFER To Fig 8a 9 09833410 Figure 7a Autoanswer Flowchart 28 PRELIMINARY AM79101 DATA SHEET Figure 7b Autoanswer Timings Table 4 DTMF Tone Combinations High Group Frequencies Hz 1209 1336 1477 Low Group Frequencies Hz 29 PRELIMINARY AM79101 DATA SHEET DATA TRANSMISSION Full Duplex Following call establishment full duplex data transmission can be started by either the called or calling modem If the connection has been established and the modem is looping through point A in Figure 8a it no longer matters which is the called and which is the calling modem Data transmission is initiated by setting REQUEST TO SEND RTS LOW At this time the TRANSMITTED DATA TD input will be released and a modulated carrier can appear at the TRANSMITTED CARRIER TC output Following a delay trcon CLEAR TO SEND CTS changes to LOW At this time data may be transmitted through TD It is common protocol for the user to always present a Mark at TD before RTS is asserted and during the treoy delay Data transmission continues until RTS is set HIGH Following a short delay tpcorp CTS changes to HIGH As soon as RTS goes HIGH TD is ignored and TC is set to 0 0 Volts silence
18. Speed option if applicable Package type d Temperature range e Optional processing Am79101 D i e Optional Processing Blank Standard processing B Burn in d Temperature Range C Commercial 09C to 709 I Industrial 409C to 8590 E Extended 559C 12590 Package D 28 Pin Ceramic DIP CD 028 P 28 Pin Plastic DIP PD 028 J 28 Pin PLCC PL 028 amp AMD Device Type b Speed Option FSK Modem Not Applicable Valid Combinations Am79101 DC DCB DI DIB PC DE DEB JC Valid Combinations Valid Combinations list configurations planned to be supported in volume for this device Consult the local AMD sales office to confirm availability of specific valid combinations to Check on newly released valid combinations and to obtain additional data on AMD s standard military grade products PRELIMINARY AM79101 DATA SHEET PIN DESCRIPTION All digital inputs and outputs are TTL compatible unless other wise noted SETUP CONTROLS DA C Data Call Input This input selects the Data Mode DA CA HICH or the Call Mode DA CA LOW In the Data Mode the Am79101 operates as a modem using other setup and handshake inputs Data Mode is the initial condition by default To enter the Call Mode DA CA is brought to a LOW while DIR is HIGH and MC pins are set to a valid mode i e not reserved mode Once in the Call Mode DTR is set LOW MC inputs and RTS w
19. ack ERAI EBERT eds All Bell 202 modes and 23 Soft Turn off modes Soft Turn off Tone gt 900 Hz BRTS LOW and BTD HIGH 387 Hz at TC BRTS HIGH or BTD LOW O Volts at TC 387 Hz at RC BCD LOW No 387 Hz at RC BCD HIGH Call Establishment The Am79101 supports Autodial and Autoanswer with the following features Call Progress Tone Detection CPTD Dual Tone Multi Frequency DTMF Tone Generation Answer Tone Detection ATD Answer Tone Generation ATG 23 PRELIMINARY AM79101 DATA SHEET First the Mode Control MCg MC4 pins are used to set up the modem mode Next the Call Mode is entered by setting DA CA LOW see pin description DTR is then set LOW once at the beginning of the Autodial or Autoanswer sequence RTS remains HIGH except when tones are required to be transmitted Now the MC pins can be used to select the above Autodial Autoanswer features as defined in Table 1b Autodial begins by using the CPTD function to detect the proper dial tone from the central office The DTMF digit to be dialed is then input to the MC pins and the transmitter generates the corresponding DTMF tones at the TC pin After the last digit is sent CPTD is used again to detect the ringback signal Following the detection of ringback the ATD feature can be used to detect the answer tone from the called moden Following detection of the correct answer tone data
20. al and digital to analog functions are provided on chip Using the features described here an intelligent Autodial Autoanswer FSK modem may be implemented with only an Am79101 single chip under the control of a host microprocessor and a Data Access Arrangement DAA circuit The modem operates in a serial asynchronous mode the serial interface supports the RS 232C CCITT V 24 type handshake signals at TTL levels The modem analog interface provides an internal hybrid for the 4 to 2 wire conversion Auxiliary functions performed within the Am79101 include Autodial support with generation and Call Progress Tone Detection Answer Tone Detection Bell and CCITT Autoanswer support Analog loopback support The Am79101 is housed in a 28 pin plastic leaded chip carrier as well as 28 pin plastic and ceramic dual in line packages Connection to the telephone network may be via a DAA or an acoustic coupler All digital I O signals are TTL compatible except the external clock and RESET signals and the circuit operates from 5 Volts 1444 Am79101 Block Diagram 6 PRELIMINARY AM79101 DATA SHEET DIP Note Pin 1 is marked for orientation PRELIMINARY AM79101 DATA SHEET ORDERING INFORMATION Standard Products AMD products are available in several packages and operating ranges The order number valid combination is formed by a combination of the following a Device number b
21. bility for the use of any circuits described herein 1988 Advanced Micro Devices Inc WCP 5M 2 88 0 WWW ALLDATASHEET COM Copyright O Each Manufacturing Company All Datasheets cannot be modified without permission This datasheet has been download from www AllDataSheet com 10096 Free DataSheet Search Site Free Download No Register Fast Search System www AllDataSheet com
22. e Call Mode DTR does not have to be changed when going from one DTMF digit to another MCo9 MC4 Mode Controls Inputs In the Data Mode the MC inputs specify one of the 25 available modem configurations as listed in Table 1a Included are Bell 103 202 CCITT V 21 V 23 with various options like equalizer 150 bps back channel soft turn off and loopback The loopback modes set the signal processing frequency band of the receiver to that of the transmitter The user must connect TC to RC for analog loopback and RD to TD for digital loopback as shown in Figure 1l In the Call Mode the MC inputs select generation of DTMF or answer tones or detection of call progress tones or answer tones as listed in Table lb None of the reserved modes should be used TRANSMITTER I O BCTS Back Clear To Send Output This line is equivalent to CTS for the main channel except that it applies only to the back channel BCTS is meaningful only when a V 23 mode or 202 150bps or 75bps back channel mode is selected by MCo MC4 This signal is not used in the 202 5bps back channel mode 10 PRELIMINARY 147 9 10 1 DATA SHEET BRTS Back Request To Send Input BTD RTS Since the 1200bps modem configurations Bell 202 and CCITT V 23 permit only half duplex operation over 2 wire lines a low baud rate back channel is provided for simultaneous transmission in the reverse direction BRTS is directly equivalent to main channel RTS except that
23. e DTMF tone duration and the interdigit interval Inputs to the MC pins should be changed while RTS is HIGH and DTR is LOW Answer Tone Detection ATD The Am79101 receiver can detect answer tones for the Bell 103 202 and CCITT V 21 V 23 modes CD LOW indicates the presence of a valid answer tone RD distinguishes between the three answer tones as shown below This feature allows mode matching with the remote modem In the CCITT V 21 V 23 modes X at RD indicates toggling between HIGH and LOW Modem Mode Answer Tone Frequency Hz CD RD Bell 103 2225 LOW HIGH Bell 202 2025 LOW LOW CCITT V 21 V 23 2100 LOW X The Carrier Detect Call thresholds Vcpcorr for valid answer tone detection are internally set to be higher than those in the Data Mode This eliminates the need for external attenuator in the Call Mode to prevent noise from being decoded as an answer tone Answer Tone Generation ATG Answer tones are generated according to the modem mode Selected as listed in the ATD section RTS LOW controls the answer tone duration and RTS HIGH controls the silence intervals Silence interval before the answer tone is required by various governmental agencies for billing delay purposes 25 PRELIMINARY AM79101 DATA SHEET START START RTS REMAINS HIGH FOR SILENCE DUR Fig 8 or 9 Figure 6a Autodial Flowchart 26 PRELIMINARY AM79101 DATA SHEET 6077960 suu e poyny 99
24. for at least 1 us as shown in Figure 155 Figure 15b Reset Timing Diagrams Upon device initialization or mode change DTR must be brought HIGH for a time tysy 2100 microseconds as shown in Figure 16 MC DESIRED MODE tusu Figure 16 Mode Setup POWER SUPPLY For maximum performance power supply bypassing should be used VCC should be decoupled to DGND and VBB to AGND as shown in Figure 17 The 0 01 uF ceramic disc capacitors should be mounted as physically close to the pins as possible 45 PRELIMINARY AM79101 DATA SHEET 35 Vdc Figure 17 Power Supply Connections ABSOLUTE MAXTMUM RATINGS Storage Temperature 65 to 1259 Ambient Temperature with Power Applied Commercial C Devices 0 to 7090 Industrial I Devices 40 to 859C Extended E Devices 55 to 12596 Vee with Respect to DGND 6 V 4 with Respect to DGND 6 V 4 V All Signal Voltages with Respect to DGND 5 Stresses above those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent device failure Functionality at or above these limits is not implied Exposure to absolutely maximum ratings for extended periods may affect device reliability Operating Ranges Positive Supply Voltage 4 75 to 5 25 V Negative Supply Voltage Vpp 4 75 to 5 25 V Commercial C Devices 0 to 7090 Industrial I Devices 40 to 859C Extended E Devices 55 to 1259 Operating ranges define t
25. h back channel the redundant transmitter components may fall in the frequency band of the local receiver channel and interfere with detection In the Am79101 these redundant and undesirable components are attenuated by digital bandpass filters Following the digital bandpass filters the filtered FSK signal is converted to an analog signal by an on chip Digital to Analog Converter DAC operating at a high sampling rate This analog FSK signal is made smooth by a simple on chip analog low pass filter In the Call Mode the sine synthesizer generates the DTMF or answer tones as specified by the MC inputs These tones are then processed like the FSK signal and eventually appear at TC Table 4 shows the DTMF tone combinations Receiver Demodulator A simplified block diagram of the Am79101 FSK receiver is shown in Figure 3 Data transmitted from a remote site modem over the phone line is a FSK modulated analog carrier This carrier is applied to the RECEIVED CARRIER RC pin via a DAA or an acoustic coupler The first stage of the demodulator is a simple on chip analog low pass anti alias filter The output of this is converted into digital form and filtered by digital bandpass filters to improve the signal to noise ratio and reject other independent channel frequencies associated with the phone line in the case of full duplex configuration In the Data Mode the bandpass filtered output is digitally demodulated to recover the binary data to
26. hose limits over which the functionality of the device is guaranteed 46 PRELIMINARY AM79101 DATA SHEET DC CHARACTERISTICS over operating ranges unless otherwise specified Digital Inputs DA CA MCg MC4 DIR RTS BRIS TD RESET Digital Outputs CTS BCTS CD BCD RD BRD Para Test meters Description Conditions Min Units gt 400 uA 50 pF Toy 2 mA Crp 50 pF C I Devices um 20 v E Devices 11 External Clock Input LOW External Reset Input HIGH RESET VILR External Reset Input LOW RESET v Input HIGH Voltage 11 Digital Input Leakage 0 0 lt Vin lt 10 10 Current 0 0 lt lt EN ps 47 Reset Input Leakage Current 1 0 PRELIMINARY AM79101 DATA SHEET DC CHARACTERISTICS Continued Supply Current Supply Cour Output Capacitance Power Test Supply Description Conditions Min Vec Negative Supply Voltage CIN Input Capacitance Standard Load Circuit POINT voc Notes 1 Cj 50 pF including stray and wiring capacitance FROM D4 2 All diodes 183064 OUTPUT 1960 01 or equivalent 02 3 All resistors are 1 8 watt 1 3 4 Vec 5 Volts 5 D 48 PRELIMINARY AM79101 DATA SHEET SWITCHING CHARACTERISTICS DTMF and ATG Output Description Typical
27. ill be sent during the time CTS goes HIGH at the end of a delay initiated when RTS goes HIGH trcoFF CTS will never be LOW when DTR is HIGH Request To Send Input A LOW on this input instructs the modem to enter transmit mode This input must remain LOW for the duration of data transmission This signal has no effect if DTR is HIGH disabled A HIGH level on this input turns off the transmitter 11 PRELIMINARY 117 9 3 01 DATA SHEET In the Call Mode RTS also controls the transmitter When RTS is LOW the tone specified by the MC pins will be transmitted A HIGH level will turn off the tone During Answer Tone Detection and Call Progress Tone Detection RTS should be HIGH TC Transmitted Carrier Output Non TTL Compatible This analog output is the modulated carrier to be sent over the phone line Its frequency changes according to the data at TD or BTD TD Transmitted Data Input Data bits to be transmitted are presented to this input serially HIGH Mark corresponds to logic 1 and LOW Space corresponds to logic 0 This input determines which frequency to appear at any instant at TC See Table 3 No signal appears at TC unless DTR is LOW and RTS is LOW RECEIVER I O BCD Back Carrier Detect Output This line is equivalent to CD for the main channel except that it applies only to the back channel BCD is meaningful only when 202 or V 23 mode is selected by MCg MC4 For the V 23 or 202 l50bp
28. ill determine the generation of either DTMF or answer tones and the detection of call progress tones or answer tones To re enter the Data Mode DA CA is returned to a HIGH during a valid modem mode DTR Data Terminal Ready Input A LOW level on this input indicates the data terminal is ready to send and or receive data via the modem This signal is gated with all other TTL inputs and outputs so that a LOW level enables these signals as well as the internal control logic A HIGH disables all TTL I O pins and the internal logic When DTR is HIGH the modem handshake state machine is reset to initial conditions This is the only way to reset the state machine and must be done after power up The state machine does not automatically power up to a known state If DTR is permanently enabled LOW the state machine will simply run from wherever it powers up This can result in abnormal behavior such as an unusually short RTS CTS delay due to lack of DTR initialization PRELIMINARY AM79101 DATA SHEET To change the modem mode when powered up use the following sequence See Figure 16 1 Set DTR HIGH 2 Change MC inputs to desired configuration 3 Wait at least 100 microseconds 4 Set DTR LOW The MC inputs perform some hardware functions and are also sampled periodically by the state machine If the inputs are changed vithout re initialization using DTR the state machine will not completely change to the new mode In th
29. it applies only to the back channel Note that since the modem contains a single transmitter RTS and BRTS should not be asserted simultaneously BRTS is meaningful only when a 202 or V 23 mode is selected by 0 4 In all other modes it is ignored For the V 23 modes and the 202 150bps or 75bps back channel mode the frequency appearing at TC is determined by a Mark or Space at BTD For the 202 5bps back channel mode a frequency of 387 Hz appears at TC when BRTS is LOW and BTD is HIGH No energy 0 0 Volts appears at TC when BRTS is HIGH BTD should be held HIGH in this mode BRTS then is equivalent to the transmitted data BRTS is the Secondary Request to Send for 202 S T modems or the Supervisory Transmitted Data for 202 C D modems Back Transmitted Data Input This line is equivalent to TD for the main channel except that it applies only to the back channel BTD is meaningful only when a 202 or V 23 mode is selected by MCg MC4 For 202 Sbps back channel transmission of On off keying BTD should be set HIGH Clear To Send Output This output goes LOW at the end of a delay trcon initiated when RTS goes LOW Actual data to be transmitted should not be presented to TD until a LOW is indicated on CTS This gives the receiving modem on the other end of the phone line enough time to recognize a valid carrier signal before data is transmitted Normally the user should force TD HIGH whenver CTS is HIGH so a Mark w
30. k channel signals are non functional Figures 8a through 9 depict the sequencing of the two state machines State machine 1 implements main or back channel transmission State machine 2 implements reception on main or back channel Table 5 lists the timing parameters and Figures 10 through 13 show the handshake timing diagrams for the various modem modes The state machine powers on to the state labeled INITIAL CONDITIONS Handshake signals are set to or assumed to be the levels listed in Table 2 The machine then waits for DATA TERMINAL READY DTR to go LOW Whenever DTR is changed from LOW to HIGH each state machine and external signals return to the initial conditions within 25 microseconds After DTR is set LOW the Am79101 becomes operational as a modem and the state machines proceed as depicted in the flowcharts The definitions of the terms full duplex and half duplex used in these flowcharts are depicted in Figures 4 and 5 Full duplex applies to all 103 113 and V 21 modes Half duplex applies to 202 and V 23 both main and back channels Full Duplex Data can be transmitted and received simultaneously at 300 bps Two independent 300 Hz channels are frequency multiplexed into the 3000 Hz bandwidth of the phone line The Am79101 configurations for the Bell 103 113 and CCITT V 21 can be operated full duplex Half Duplex In half duplex with back channel the Am79101 may transmit at 1200 600 bps and receive at 5 75 150 bps Alter
31. m8051 and the dual channel Serial Communication Controller AmZ8530 The AmZ8530 can also be used in other CPUs such as Z80 8080 6800 and 68000 The internal hybrid of the Am79101 performs the 4 to 2 wire conversion to simplify the user interface to the switched telephone network The analog signals TC and RC are coupled directly into the DAA circuit as shown in Figure 22 For additional information refer to AMD s 1987 Modem Technical Manual PID 09560 Am79101 See Figure 22 Figure 20 300 bps Full Duplex Modem 53 095334 25 PRELIMINARY AM79101 DATA SHEET 1 08 See Figure 22 ck Channel 1200 bps Half Duplex Modem with 75 150 bps Ba Figure 21 54 PRELIMINARY AM79101 DATA SHEET TC RC RING IND Figure 22 Data Access Arrangement PHYSICAL DIMENSIONS 55 PRELIMINARY AM79101 DATA SHEET PD 028 36 E J 28 PL 028 56 ADVANCED MICRO DEVICES NORTH AMERICAN SALES OFFICES 202 882 9122 602 242 4400 213 645 1524 714 752 6262 619 560 7030 408 249 7766 408 727 3270 i 818 992 4155 CANADA Ontario Kanata 613 592 0060 Willowdale 416 224 5193 COLORADO 803 741 2900 CONNECTICUT 203 264 7800 FLORIDA Clearwater 813 530 9971 Ft Lauderdale 208 776 2001 Melboume 305 729 0496
32. mit CD HIGH output indicates there is no energy above the Vcpcorr RC Received Carrier Input Non TTL Compatible This input is the analog signal received from the phone line The nodem extracts the information contained in this modulated carrier and converts it into a serial data stream at RD or BRD RD Received Data Output Data bits demodulated from RC are available serially at this output HIGH Mark indicates logic 1 and LOW Space indicates logic 0 Under the following conditions this output is clamped HIGH because the data may be invalid 1 When CD is HIGH 2 During the internal squelch delay at half duplex line turn around 202 and V 23 modes only 3 During soft carrier turn off at half duplex line turn around 202 and V 23 soft turn off modes only 4 When DTR is HIGH 5 When RTS is LOW and BRTS is HIGH in 202 and 23 modes only 6 During Autoanswer sequence MISCELLANEOUS AGND Analog Ground 13 PRELIMINARY AM79101 DATA SHEET CAP1 CAP2 Non TTL Compatible These two pins are connection points for the external series capacitor resistor required for proper operation of the on chip analog to digital converter Recommended values are 2000 pF 10 910 ohm 105 DGND Digital Ground RESET Non TTL Compatible This input signal is for a reset circuit which operates in either of two modes refer to Figures 15a and 15b The Am79101 should be reset upon initial application
33. nately it may transmit at 5 75 150 bps and receive at 1200 600 bps Examples are Bell 202 and CCITT V 23 Table 2 Initial Conditions Data Call DA CA HIGH Data Data Terminal Ready DTR Request to Send RTS Clear to Send CTS Transmitted Data TD Ignored Back Channel Request to Send BRTS HIGH Back Channel Clear to Send BCTS HIGH Back Channel Transmitted Data BTD Ignored Carrier Detect CD HIGH Received Data RD HIGH Back Channel Carrier Detect BCD HIGH Back Channel Received Data BRD HIGH 21 PRELIMINARY AM79101 DATA SHEET 2 BELL 109114 sea 11900 1650 1 1850 1070 1270 2025 1040 1750 1170 5252225 FREQUENCY FREQUENCY Hz Figure 4 Full Duplex Channel Assignments Cam v21 7 2 zu 17 420 ys FREQUENCY Hz FREQUENCY BELL 202 5 bpe BACK BEL 202 160 bps BACK 1200 1700 2200 387 2200 1709 FREQUENCY riz FREQUENCY Hz Figure 5 Half Duplex Channel Assignments 22 PRELIMINARY AM79101 DATA SHEET Table 3 Frequency Parameters Transmit Receive Frequency Frequency Baud Rate Space Space Modem Mode bps Duplex Hz Hz Bell 103 Answer E Full ee 1270 3 CCITT V 21 Originate 1180 1850 1650 CCITT V 21 Answer 1850 1650 1180 CCITT V 23 Mode 2 1200 2100 1300 2100 CCITT V 23 Mode 2 Equalized 1200 Half 2100 1300 2100 1300 er V 23 B
34. pears at TC when BRTS is HIGH 0 0 Volts appear at TC DATA RECEPTION Data reception is controlled by state machine 2 and depicted in Figure 9 At power on the machine enters initial conditions and remains there until DTR is set LOW It then loops until either CARRIER DETECT CD LOW or BACK CARRIER DETECT BCD LOW occurs Full Duplex In full duplex data reception carrier may appear at any time after the phone connection has been established Reception is independent of transmission When the receiver detects a valid carrier for at least the time the output CD goes LOW and valid data can be obtained at RD Data is received until the receiver detects loss of carrier for at least the time tcporr At this time CD goes HIGH and RD is clamped to a Mark The state machine returns to the idle loop at point E Half Duplex As discussed in the Data Transmission section when a half duplex mode has been selected RTS controls whether the main channel is transmitting or receiving The back channel can only do the opposite from the main channel If RTS is HIGH CD may be activated and the data reception sequence is identical to that discussed above for full duplex reception s long as RTS remains HIGH BCD will never be activated If RTS is LOW then CD will never be activated Instead the receiver will look for a valid carrier in the back channel frequency band If a valid carrier exists for at least the time
35. r baud logic 1 applied to the TRANSMITTED DATA TD input causes a sine wave at a given frequency to appear at the analog TRANSMITTED CARRIER TC output A logic 0 applied to TD causes a sine wave of a different frequency to appear at TC As the data at TD switches between logic 1 and 0 TC switches between the two frequencies In the Am79101 this switching between frequencies is phase continuous The frequencies themselves are digitally synthesized sine functions The frequencies for each modem configuration available in the Am79101 are listed in Table 3 The process of switching between two frequencies as in FSK generates energy at many more frequencies than the two used in the modulation A11 the transmitted information can be recovered from a frequency band B Hz wide where B is the bit rate or maximum rate of change of the digital data at TD This band is centered about a frequency fc where fc fj f2 2 fi lower of two FSK frequencies 82 higher of two FSK frequencies 18 PRELIMINARY AM79101 DATA SHEET In addition to this primary information band there are side bands containing redundant information It is desirable to attenuate these bands for two reasons 1 The phone companies have specifications on the amount of energy allowed in certain frequency bands on tbe line 2 If two independent information channels are present simultaneously on the line e g 300 bps full duplex or 1200 bps half duplex wit
36. r than the Oscillator SERI N ll lt lt 444 01 0 1 02 10 10 0 100 09633 23 Figure 19 Out of Band Transmitter Energy APPLICATIONS An intelligent Autodial Autoanswer FSK modem can be easily built with the Am79101 Figures 20 and 21 show implementations of full duplex and half duplex modes For the full duplex 103 V 21 modes a single baud rate 300 bps is used With its on chip UART the single chip microcontroller Am8051 provides a simple solution The Am79101 s RS 232C signals and setup controls are connected to the Am8051 as shown in Figure 20 MC conveniently controls the on hook relay in the DAA circuit MC4 0 activates off hook and MC4 1 keeps on hook during analog loopback for local testing If DTMF dialing is not permitted on a particular telephone network the relay contact can be rapidly made and broken for pulse dialing Automatic answering of incoming calls is serviced like an interrupt routine by the Am8051 Upon ringing the DAA interrupts the Am8051 which then places the relay off hook and the Am79101 in the Call Mode to generate the answer tone After the call is established or answered the Am8051 has complete control to start data transfer 52 PRELIMINARY AM79101 DATA SHEET For the half duplex 202 V 23 modes two different baud rates 1200 bps and 75 150 bps are used for the main and back channels dual UART system is required Figure 21 shows an implementation with the A
37. s or 75bps back channel modes BCD changes to LOW when either the Mark or Space frequency appears with sufficient level at RC For the 202 5bps back channel mode BCD changes to LOW in response to a 387 Hz tone of sufficient level at RC In this case BCD is equivalent to the signal Secondary Received Line Signal Detector for 202 8 5 modems or Supervisory Received Data for 202 C D modems BRD Back Received Data Output This line is equivalent to RD for the main channel except that it applies only to the back channel BRD is meaningful only for the V 23 or the 202 back channel modes Under the following conditions this output is clamped HIGH 1 21 103 modes 2 BCD HIGH DTR HIGH 4 BRTS LOW and RTS HIGH in V 23 or 202 150 bps modes only 5 During Autoanswer sequence 12 PRELIMINARY AM79101 DATA SHEET CD Carrier Detect Output A LOW on this output indicates that a valid carrier signal is present at the receiver and has been present for at least the time A HIGH on this output signifies that no valid carrier is being received and has not been received for at least the time tepopr In the Data Mode Carrier Detect looks for energy in the receive bandwidth A carrier is considered valid when the signal level at RC is above a threshold limit Vcpow and absent when the level is below Vcporr In the Call Mode a CD LOW output indicates a valid answer tone or call progress tone has been detected above the li
38. tinued MC4 MC3 MC2 MC MCo o Bell 103 Originate loopback Bell 103 Answer loopback Bell 202 main loopback Bell 202 with amplitude equalizer loopback CCITT V 21 Originate loopback CCITT V 21 Answer loopback CCITT V 23 Mode 2 main loopback CCITT V 23 Mode 2 with amplitude equalizer loopback CCITT V 23 Mode 1 main loopback CCITT V 23 back loopback Bell 202 150 bps back loopback 0 0 0 1 1 1 1 0 0 0 0 Up to 150 bps back channel is available Note Reserved modes should not be entered 16 PRELIMINARY 117 9101 DATA SHEET Table lb Mode Controls in the Call Mode DA CA LOW HMC4 MC MCo Autodial Autoanswer Function 0 or Answer Tone Detection 103 Answer Tone 202 Answer Tone or V 23 Answer Tone Progress Tone Detection Reserved Note Reserved modes should not be entered 17 PRELIMINARY 79101 DATA SHEET Figure 1 Loopback Configurations FUNCTIONAL DESCRIPTION The modem consists of three main sections shown in the Am79101 block diagram Transmitter Receiver and Interface Control Transmitter Modulator In the Data Mode the transmitter shown in Figure 2 receives binary digital data from a source such as a UART and converts the data to an analog signal using Frequency Shift Keying FSK modulation This analog signal is applied to the phone line through a DAA or an acoustic coupler FSK is a modulation technique which encodes one bit pe
39. ved at the remote modem During soft turn off the modem transmits a soft carrier frequency for a period after RTS goes HICH This results in a steady Mark on the RECEIVED DATA RD line of the remote modem Squelch The local receiver must be turned off after RTS is HIGH until the start of carrier detect so that line transients are not demodulated The process of disabling the receiver after RTS goes HIGH is called squelching Back Channel This transmission sequence shown in Figure 8b is entered if a 202 or V 23 mode is selected RTS is HIGH and BRTS is asserted The BACK CARRIER DETECT BCD output is forced HIGH and the BACK RECEIVED DATA BRD output is clamped to a Mark The BACK TRANSMITTED DATA BTD input is released and a carrier appears at the TC output which follows the Mark Space applied to Setting BRTS LOW initiates a delay at the end of which the BACK CLEAR TO SEND BCTS output goes LOW When BCTS goes LOW data may be transmitted through BTD Data transmission continues until BRTS is set HIGH BTD is immediately ignored and TC is silenced set to 0 0 Volts Following a short delay tpgcorr BCTS goes HIGH The signals BCD and BRD are released and the state machine returns to idle at point A of Figure 8a In 202 5 bps back channel mode 810 31 PRELIMINARY AM79101 DATA SHEET should be tied HIGH Then BRTS controls the On Off keying modulation When BRTS is LOW a 387 Hz tone ap
40. ved from one of several crystal driven baud rate generators It should be connected to XTAL and XTAL must be left floating The timing parameters required of this clock are shown in Figure 145 and the values are listed in Table 6 Crystal Information f 2 4576 MHz Manufacturer M Tron Monitor Products Note Rise time of must be greater than 5 ms to insure proper crystal oscillator start up CLOCK XTAL NC XTAL Capacitor values vary with different crystal manufacturers The input impedance of this pin appears as 5 to 10 pF to ground in parallel with at least 1 Megohm Fiqure 14a Clock Generation 43 PRELIMINARY AM79101 DATA SHEET Q96334 19 Figure 145 External Clock Table 6 Clock Parameters pope Period 406 86 406 94 tcr Clock Fall Time 75 27 RESET MODES Automatic Power On Reset Figure 15a suggests a circuit to initiate the internal reset sequence automatically whenever is applied Vcc rise time should be faster than one half the RC time constant The Am79101 contains a diode to discharge the capacitor when gt 0 V Figure 15a Automatic Reset 44 PRELIMINARY 79101 DATA SHEET RESET Input The Am79101 can be forced into the internal reset sequence by setting RESET LOW for at least one clock period Note that must be at least 43 5 V for proper reset operation Between repetitive reset pulses RESET must be HIGH
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