nov 24 4991 aati Am7910/11 WORLD-CHIP FSK Modem cl Advanced Micro Devices DISTINCTIVE CHARACTERISTICS Common Capabilities = Complete FSK Modem in 28-pin package = Commercial, industrial and Extended temperature ran = 300-bps full-duplex operation perature range B No external filtering required @ 1200-bps half-duplex operation : All digital signal processing, digital filtering, 1200-bps full-duplex on four-wire and A/D-D/A conversion on-chip Compatible with Bell 103/113/108, Bell 202, includes essential RS-232/CCITT V.24 CCITT V.21, and V.23 handshake signals on-chip @ Available in CDIP, PDIP, and PLCC packages Autoanswer capability Unique Device Capabilities Am7910 Am7911 Dial-up network response times @ Fast response time for leased-line networks Bell 202 with 5-bps back channel @ Bell 202 with 5-bps or 150-bps back channel V.23 with up to 75-bps back channel @ YV.23 with up to 150-bps back channel BLOCK DIAGRAM CAP1 oe Rp + FF prareg UU ae BRD #+ Demodulator Analog BD + To 7 > VDD 7 > . TUL Modulator BID a 4 Al Ti Generator + 0m 7 -4- Fis Mt M ty Intertace| > CTs NC3 > Control BRTS aa E } BCTS RESET XTALVCLK XTAL2 VOC VBB AGND DGND 09833C-001 WORLD-CHIP is a registered trademark of Advanced Micro Devices, Inc. / Publication # 04262 Rev. D Amendment 0 Issue Date: June 1989GENERAL DESCRIPTION Advanced Micro Devices offers a family of high- performance FSK modem chips that may be easily inte- grated in system designs to interface terminals and workstations to the Telephone Network. The product family consists of: Am7910 FSK Modem -Am7911 FSK Modem ~Am79101 Autodial FSK Modem Am7910 and Am7911 AMD currently offers three single-chip modems in the Frequency Shift Keying (FSK) series including the Am7910, the Am7911 and the Am79101. This family of modems includes most of the building blocks required for a complete communication system. Some of the on-chip features include: analog-to-digital and digital- to-analog converters, internal crystal oscillator, and the essential RS-232/CCITT V.24 terminal contro! signals with TTL levels. A DAA (Data Access Arrangement) or acoustic coupler must be supplied externally to provide the Phone Line Interface. The FSK modem chips all have the same basic structure as shown in the simplified block diagram. The Am7910 and the Am7911 differ mainly in timing parameters with the Am7911 being tailored for better performance in leased-line, multidrop applications. The Am7911 also includes an extended set of modem selection modes. The Am79101 is described in a separate data sheet (order no. 09833). 2 Am7910/11TABLE OF CONTENTS Distinctive Characteristics ... 0.0.0.6... ete tence eee teen eneneee 1 General Description ... 02.0.0 cc cece ce eee tenet ene eenennaes ..2 Connection Diagram ....... cece eee ee eee etre eee ene 4 Ordering Information ......0 0. cc cc ccc eee ete eee renee teenies 5 Pin Description .. 2.0... 0. cece eee eee ee een een ease netaanes 6 Functional Description ....... 0.02 cece eect eee cee eee teen eee ee nee 10 Call Establishment ... 0.0... cee eee reenter en eee tenets 14 Data TransmISSION .. 0.0... ce eee ete ee eee ttc ee ee teeter eeeaeane 16 Full-Duplex . 2... ccc ee eee ee ee eee eater eee ween sere reseras 16 Half-Duplex 2... ee cece eee eee e eee ee eee eee nen eneete 16 Main Channel .. 2... 0. ccc cee eee rere te eee neers ee tenes 16 Back Channel... 0. ccc ete eee ee teeter eee ene terran enees 16 Data Reception .... 0... ccc ce cece ete ee eee eee eee eens eennes 19 Full-DUplex . 0 ce ee tee ee eee ene tree net ee ene enaee 19 Half-Duplex 2... ccc cece ccc eee ee eee tener ete eee en ene eet eneenenene 19 Timing Parameters 2.1... 0... cece cent tee eee eee eee nnenenes 21 LOOPHDACK 2.1... eect eee ee een enter e ee tenon eens 27 Clock Generation... 0. ccc ee eee tenet e teen enereneee 27 Absolute Maximum Ratings .......... 0... cee cece ee erent tees 30 Operating Ranges ...... 0... ccc cee ee eee eee teen e ee ne tenes 30 DC Characteristics ....... 0... e ccc ene tere center ee etna 31 Switching Characteristics ......... 00s ccc eee eee eee teen nee 33 Applications ........ 0. cece ce eee eee eee te teen eee et ee eeraenes 35 Physical Dimensions ......... 000 c cece eter e renee nee eae teen tenons 39 Am7910/11CONNECTION DIAGRAMS Top View 28-Pin DIP LI RING] 1 28 {_] BTD vec] 2 27 (_] BCD RESET(] 3 26 [_] RD vBBL] 4 25 [7] cD rcC] 5 24 [_] XTAL1/CLK CAPIT] 6 23 [[] xTAL2 cap2(] 7 22 [_] DGND ToC] 8 21 [_] Mc4 AGND [7] 9 20 [-] mca TOL] 10 19 [_] Mc2 BATS 11 13 (-] Mct RIS(] 12 171") Mco esl 13 16[-] DTR BcTsL 14 45 [_] BRD Note: Pin 1 is marked for orientation. 28-Pin PLCC i LL 1S. a ) Q a a s Sf & B & Ci fi ti fit) C1 I 4 3 2 1 28 27 2 e RC [| 5 25 7 GD capi[_| 6 24 |] XTALWV/CLK cap2 [| 7 23 [_] XTAL2 te[_]|8 22 |_] OGND acnp [_] 9 21 [7] Mca To [_] 10 20[_] Mcs pars [| 11 19|_] Mc2 1213 14 15 ~=16 17 _~=*18 CLI CUPtI CUI EJ Wi ud 2 i a r Eb & & & 8 09560-3B Am7910/11ORDERING INFORMATION Standard Products AMD standard products are available in several packages and operating ranges. The ordering number (Valid Combination) is formed by a combination of: AM7910/11 D c 8 a. Device Number b. Speed Option (if applicable) c. Package Type d. Temperature Range e. Optional Processing CL o. OPTIONAL PROCESSING Blank = Standard Processing B = Burn-in d. TEMPERATURE RANGE C= Commercial (0C to +70C) 1 = Industrial (40C to +B5C) E= Extended (-55C to +125C) c. PACKAGE TYPE a. DEVICE NUMBER/DESCRIPTION Am7910/11 WORLD-CHIP FSK Modem P= 28-Pin Plastic DIP (PD 028) D= 28-Pin Ceramic DIP (CD 028) J = 28-Pin PLCC (PL 028) b. SPEED OPTION Not Applicable Valid Combinations AM7910 PC, JC, DC, AM7911 DCB, Di, DIB, DE, DEB Valid Combinations Valid Combinations list configurations planned ta 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 combinations, and ta obtain additional data on AMD's standard military grade products. Am7910/11PIN DESCRIPTION All digital inputs and outputs are TTL-compatible unless otherwise noted. Setup Controls AGND Analog signal ground pin (for TRANSMITTED CARRIER and RECEIVED CARRIER). BCD Back Carrier Detect This line is equivalent to CD for the_main channel, except it belongs to the back channel. BCD is meaning- ful only when a 202 or V.23 mode is selected by MCO- MC4. For the V.23 back channel mode or the 202 150-bps (or 75-bps) back channel mode, BCD activates when either the Mark or Space frequency appears with sufficient level at the RC (Received Carrier) input. For the 202 5-bps back channel mode, BCD turns on in response to a 387 Hz tone of sufficient level at the RC input. In this case BCD is equivalent to the secondary received line signal detector for 202 S/T modems, or supervisory received data for 202 C/D modems. BCTS Back Clear to Send This line is equivalent to BCTS for the main channel, except it belongs to the back channel. BCTS is mean- ingful only when a V.23 mode or 202 150-bps (or 75-bps) back channel mode is selected by MCO-MC4. This signal is not used in the 202 5-bps back channel mode. BRD Back Received Data This line is equivalent to RD for the main channel, except that it applies only to the back channei. BRD is meaningful only for the V.23 or the 202 back channel modes. Under the following conditions this output is clamped High: B V.21/103 modes BCD High @ DIR High @ BRTS Low and RTS High in V.23 or 202 150-bps modes only During autoanswer sequence. BRTS Back Request to Send Since the 1200-bps modem configurations (Bell 202 and CCITT V.23) permit only half-duplex operation over two-wire lines, a low baud rate back channel is provided for simultaneous transmission in the reverse direction. BRTS is equivalent to RTS for the main channel, except that it belongs to the back channel. Since the modem contains a single transmitter, RTS andBRTS should not be asserted simultaneously. BRTS is meaningful only when a 202 or V.23 mode is selected by MCO-MC4. In ail other modes, it is ignored. For the V.23 modes and the 202 150-bps (or 75-bps) back channel mode, the frequency appearing at the TC (Transmitted Carrier) output pin is determined by a Mark or Space at the BTD input. For the 202 5-bps 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 fixed High for 202 back channel transmission. BRTS then is equivaient to the transmit- ted data. BRTS is the Secondary Request-to-Send for 202 S/T modems, or the Supervisory Transmitted Data for 202 C/D modems. BTD Back Transmitted Data This line is equivalent to TD for the main channel, except it belongs to the back channel. BTD is meaningful only when a 202 or V.23 mode is selected by MCO-MC4. For 202 5-bps back channel transmission of on/off keying, BTD should be fixed at a High level. CAP, CAP2 Connection points of external capacitor/resistor required for proper operation of the on-chip analog-to- digital converter. Recommended values are: C = 2000 pF 410%, R = 910 ohms +10%. cD Carrier Detect A Low on this output indicates that a valid carrier signal is present at the receiver and has been present for at least a time (tyo,). A High on this output signifies that no valid carrier is being received and has not been received for a time (teooer)- CD looks for energy in the receive bandwidth. CD is Low when the receive signal is above a threshold limit (V.5o,) and High when the fevel of the received signal is below Veporr- cTs Clear to Send This output goes Low at the end of a delay (tacon) initi- ated when RTS goes Low. Actual data to be transmitted should not be presented to the TD (Transmit Data) input until a Lowis indicated on the CTS output. This gives the receiving modem (on the other end of the phone line) enough time to recognize a valid carrier signal before 6 Am7910/11data is transmitted. Normally the user should force the TD input High whenever CTS i is High so a Mark will be sent during the (tacox) time. CTS goes High at the end of a delay initiated when RTS goes High (tacor:)- CTS will never be Low when DTR is High. DGND Digital signal ground pin. DTR Data Terminal Ready 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 1/0 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 pow- ers up. This can result in abnormal behavior such as an unusually short RTS-CTS delay due to lack of DTR initialization. In order to change the modem mode while the modem is powered up, use the following sequence: 1. Take DTR High 2. Change mode inputs to desired configuration 3. Wait at least 100 ps 4. Take DTA Low The mode inputs perform some hardware functions, and they are also sampled periodically by the state machine. If the mode inputs are changed without the re-initializa- tion using DTR, the state machine will not completely change to the new mode. MCO-MC4 Mode Controls The FSK modem family has multiple built-in modem modes selectable by the user through a set of Mode Control Pins. Table 1 lists the modem modes, mode- control pin states, and the product containing a particu- lar mode. The loopback modes set the receiver channel signal processing band to that of the transmit channel. No internal connection is made. The user must connect the TC pin to the RC pin if analog loopback is required (see Figure 1). For digital loopback, external connection of the RD and TD pins is required. With the Am7910/11, loopback modes can also be used to achieve full-duplex, 1200-bps communication. In CCITT V.23 or Bell 202 loopback modes, the modem can transmit and receive at 1200 bps using a four-wire configuration (transmit over one channel and receive on another). See the System Configuration section for details. RC Recelved Carrier This input is the analog signal received from the phone line. The modem extracts the information contained in this modulated carrier and converts it into a serial data stream for presentation at the RECEIVED DATA (BACK RECEIVED DATA) output. RD (Received Data) Data bits demodulated from the RC (Received Carrier) input are available serially at this output; High (Mark) in- dicates logical 1 and Low (Space) indicates logical 0. Under the following conditions, this output is forced to logical 1, because the data may be invalid: When CD is High During the internal squelch delay at half-duplex line turnaround (202 and V.23 modes only) During soft carrier turnoff at half-duplex line turn- around (202 and V.23 soft turn-off modes only} When DTR is High When RTS is Low and BRTS is High in 202 and V.23 modes only During the autoanswer sequence RESET This input signal is for a reset circuit which operates in either of two modes. Refer to Figure 15 and Figure 16 for these two modes. The Am7910/11 shouldbe reset upon initial application of power. Ring This input signal permits autoanswer capability by responding to a ringing signal from a Data Access Arrangement. If aringing signal is detected (Ring = Low) and DIR is Low, the modem begins a sequence to generate an answer tone at the TC output. RTS Request to Send A Low on this input instructs the modem to enter the transmit mode. This input must remain Low forthe dura- tion of data transmission. This signal has no effect if DTR is set High (disabled). A High level on this input turns off the transmitter. Tc Transmitted Carrier This analog output is the modulated carrier to be condi- tioned and sent over the phone line. Am7910/11 7TD Transmitted Data Data bits to be transmitted are presented to this input serially; High (Mark) corresponds to logical 1 and Low (Space) corresponds to logical 0. This data determines which frequency appears at any instant at the TC (Transmitted Carrier) output pin (Table 3). No_signal appears at the TC output unless DTR is Low and RTSis Low. Veco +5-volt power supply (5%). XTALi, XTAL2z Master timing of the modem is provided by either a crys- tal connected to these two inputs or an external clock inserted into XTAL:. The value of the crystal or the exter- nal clock frequency must be 2.4576 MHz +.01%. Vas 5-volt power supply (+5%). Tabie 1. Am7910/11 Mode Control Lines 7910 7911 MC4 MC3 MC2 MCi MCO Description Xx X 0 0 0 0 0 Beli 103 originate 300 bps full-duplex x X 0 0 0 0 1 Bell 103 answer 300 bps full-duplex X X 0 0 0 1 0 Bell 202 1200 bps half-duplex x X 0 0 0 1 1 Bell 202 with equalizer x X 0 0 1 0 0 CCITT V.21 orig 300 bps full-duplex Xx X 0 0 1 0 1 CCITT V.21 ans 300 bps full-duplex X X 0 0 1 1 0 CCITT V.23 M2 1200 bps half-duplex xX X 0 0 1 1 1 CCITT V.23 M2 with equalizer X 0 1 0 0 0 CCITT V.23 M1 (1) 600 bps half-duplex x 0 1 0 0 0 CCITT V.23 M1 (2) 600 bps half-duplex 0 1 0 0 1 Reserved X 0 1 0 1 0 Bell 202 with 150 bps back channel X 0 1 0 1 1 Bell 202 with 150 bps back channel and equalizer Xx 0 1 1 0 0 CCITT V.23 M1 (2) with soft turn-off (STO) 0 1 1 0 1 Reserved x 0 1 1 1 0 CCITT V.23 M2 (2) with STO Xx 0 1 1 1 1 CCITT V.23 M2 (2) with STO and equalizer xX x 1 0 0 0 0 Bell 103 orig. joopback x X 1 0 0 0 1 Bell 103 answer loopback x xX 1 0 0 1 0 Bell 202 main loopback x Xx 1 0 0 1 1 Bell 202 with equalizer loopback xX xX 1 0 1 0 0 CCITT V.21 orig. loopback Xx x 1 0 1 0 1 CCHIT V.21 ans. loopback x X 1 0 1 1 0 CCITT V.23 M2 main loopback xX xX 1 0 1 1 1 CCITT V.23 M2 with equalizer loopback Xx x 1 1 0 0 0 CCITT V.23 M1 main loopback x 1 1 0 0 1 CCNIT V.23 (1) back loopback xX 1 1 0 0 1 CCITT V.23 (2) back loopback x 1 1 0 1 0 Bell 202 (2) back loopback 1 1 0 1 1 Reserved 1 1 1 0 0 Reserved 1 1 1 0 1 Reserved 1 1 1 1 0 Reserved 1 1 1 1 1 Reserved NOTE: Reserved modes should not be entered. (1} up to 75 baud back channel (2) up to 150 baud back channel 8 Am7910/11r Am7910/11 | l l Phone TD Te Line Digital o}+ Transmitter Loopback / | | | | Data | | Terminal RDI lac Receiver -} eS o | | Analog Lo J Loopback 09833A-3 Figure 1. Analog Loopback Am7910/11FUNCTIONAL DESCRIPTION The modem consists of three main sections shown in the block diagramTransmitter, Receiver, and Inter- face 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 per baud. A logical 1 applied to the TD input causes a sine wave at a given frequency to appear atthe analog TC output. A logical 0 applied to TD causes asine wave of a different frequency to appear at TC. As the data at TD switches between logical 1 and 0, TC switches between the two frequencies. In the AMD modem this switching between frequencies is phase continuous. The frequencies themselves are digitally synthesized sine functions. MC,-MC, Y i Digital Analog Sine JUL TD Synthesizer Bandpass DAC Fost + WT From To DAA UART Or Acoustic Coupler 09833A4 Figure 2. Transmitter Block Diagram The frequencies for each modem configuration avail- able in the FSK modem 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. All the transmitted information can be recovered from a frequency band B Hz wide. where B = bit rate or maximum rate of change of the digital data at TD. This band is centered about a frequency (fc) where fc = (f, + f,.)/2 (fs = lower of two FSK frequencies) (fe = higher of two FSK frequencies) In addition to this primary information band, there are side bands containing redundant information. It is desir- able to attenuate these bands for two reasons: 1. The phone companies have specifications on the amount of energy allowed in certain frequency bands on the tine. 2. If two independent information channels are present simultaneously on the line (for example, 300-bps full-duplex or 1200-bps half-duplex with back channel), the redundant transmitter compo- nents may fall in the frequency band of the local re- ceiver channel and interfere with detection. In the Am7910/11 these redundant and undesirable com- ponents 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 (D/A) converter operating at a High sampling rate. This analog FSK signal is made smooth by a simple on-chip analog low-pass filter. Receiver (Demodulator) A simplified block diagram of the Am7910/11 FSK receiver is shown in Figure 3. Data transmitted from a remote-site modem over the phone line is a FSK-modu- lated analog carrier. This carrier is applied to the 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 digitat 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 appear at the RD pin. ACD signal is also digitally extracted from the received line carrier to indicate valid data. The short control signal delays on the Am7911 make it attractive for use over multidrop networks. In such a sys- tem, a central site station polls a number of remote sta- tions and so the short RTS-CTS delays allow efficient line utilization when polling. 10 Am7910/11Digital at RD Analog Digital WS Rc Prefitter ADC Bandpass Demodulation [~~ | | | | From DAA TO UART Or Acousti Cb Coupe Carer | 09833A-5 Figure 3. Receiver Block Diagram Interface Control This section controls the handshaking between the modem and the local terminal. It consists primarily of de- lay-generation counters, two state machines for contral- ling transmission and reception, and mode-control-de- code logic. Proper transmit frequencies and transmit/re- ceive filters are selected according to the specified mo- dem type or function in the Data or Call mode. Inputs to and outputs from this section are as follows: Ring MCO-MC4 DTR (Data Terminal Ready) RTS (Request to Send) (Main and Back) CTS (Clear to Send) (Main and Back) ED (Carrier Detect) (Main and Back) Reset internal logic clamps the handshake signals to different levels under certain conditions (for example, initial con- ditions). When Bell 103/113 and V.21 modem configurations are selected, the back channel signals are non-functional. Figures 6 and 7 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. Tables 4 and 5 list the timing parameters, and Figures 10 through 13 show the handshake timing diagrams for the various modem modes. The state machine powers-on after reset to the state labeled INITIAL CONDITIONS. Handshake signals are set to or assumed to be at the levels listed in Table 2. The machine waits for DTA to go Low. Whenever DTR is changed from Low to High, each state machine and the external signals return to the initial conditions within 25 ms. After DIR is set Low, the Am7910/11 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 inthese 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 modes, both main and back channels. Full-DupiexData can be transmitted and received simuttaneously at 300 bps. Two independent 300-Hz channels are frequency multiplexed into the 3000-Hz bandwidth of the phone line. The Am7910/11 configura- tions for the Bell 103/113 and CCITT V.21 can be operated full-duplex. Half-Duplexin half-duplex with back channel, the modem may transmit at 1200/600 bps and receive at 5/75/150 bps. Alternately 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 Ring High DTA (Data Terminal Ready) High RTS (Request to Send) High CTS (Clear to Send) High TD (Transmitted Data) Ignored BRTS (Back Channel Request-to-Send) = High BCTS (Back Channel Clear-to-Send) High BTD (Back Channel Transmitted Data) Ignored CD (Carrier Detect) High RD (Received Data) High BCD (Back Channel Carrier Detect) High BRD (Back Channel Received Data) High Am7910/11 11Table 3. Frequency Parameters Transmit Receive Baud Frequency Frequency Rate Space Mark Space Mark Modem Mode (bps) Duplex (Hz) (Hz) (Hz) (Hz) Bell 103 Originate 300 Full 1070 1270 2025 2225 Bell 103 Answer 300 Full 2025 2225 1070 1270 CCITT V.21 Originate 300 Full 1180 980 1850 1650 CCITT V.21 Answer 300 Full 1850 1650 1180 980 CCITT V.23 Mode 1 600 Haif 1700 1300 1700 1300 CCITT V.23 Mode 2 1200 Half 2100 1300 2100 1300 CCITT V.23 Mode 2 Equalized 1200 Half 2100 1300 2100 1300 Bell 202 1200 Half 2200 1200 2200 1200 Bell 202 Equalized 1200 Half 2200 1200 2200 1200 CCITT V.23 Back 75/150 _ 450 330 450 390 Bell 202 5 bps Back 5 _ * * ** Bell 202 150 bps Back 150 _ 487 387 487 387 All Bell 202 modes and V.23 Soft Turn-off modes Soft Turn-off Tone = 900 Hz Bell 103 Answer Tone = 2225 Hz V.21 and V.23 Answer Tone = 2100 Hz Bell 202 Answer Tone = 2025 Hz * (@RTS Low) and (BTD High) : 387 Hz at TC. * (BRTS High) or (BTD Low) : 0 Volts at TC. ** 387 Hz at RC: BCD Low. ** No 387 Hz at RC: BCD High 12 Am7910/11CCITT V.21 BELL 103/113 LtVAtt LiZart 980! 1180 1650! 1850 1070! 1270 2025 | 2005 1080 1750 1170 2125 fc fe fe fe FREQUENCY (Hz) FREQUENCY (Hz) 09833A-6 Note: Full-duplex applies to all 103/113 and V.21 modes. Figure 4. Full-Duplex Channel Assignments CCITT V.23 1200 bps 600 bps tA tt Ltvztt 390 | 450 1300 |! 2100 390 | 450 1300 |! 1700 420 1700 420 1500 fe fe fe fc FREQUENCY (Hz) FREQUENCY (Hz) BELL 202 (5 bps BACK) BELL 202 (150 bps BACK) VAt ft tif tit 387 1200 1700 2200 387 08? 1200 | 2200 4 0 FREQUENCY (Hz) FREQUENCY (Hz) opega7 Note: Half-duplex applies to 202 and V.23 modes, both main and back channels. Figure 5. Half-Duplex Channel Assignments Am7910/11 13CALL ESTABLISHMENT Before two modems can exchange data, an electrical connection through the phone system must be estab- lished. Although it may assist in call establishment, a modem typically does not play a major role. A call may be originated manually or automatically and it may be answered manually or automatically. Manual CallingManual calling is performed by a per- son who dials the number, waits for an answer, then places the calling modem into data transmission mode. Automatic CallingAutomatic calling is typically per- formed by an automatic calling unit (ACU) which gener- ates the appropriate dialing pulse or dual-tone sequence required to call the remote (called) modem. The ACU also has the ability to detect an answer tone fromthe called modem and place the calling modem into data transmission mode. Manual AnsweringManual answering is performed by a person who hears the phone ring, lifts the receiver, causes the called modem to send an answer tone to the calling modem, and places the called modem into data transmission mode. Automatic AnsweringAutomatic answering is per- formed by a called modem with a data access arrange- ment (DAA). The DAA detects a ringing signal, takes the phone circuit off-hook (corresponding to lifting the receiver) and instructs the called modem to commence the autoanswer sequence. Next the called modem sends out silence on the line, followed by an answer tone. When this tone is detected by the calling modem, the connection is considered to have been established. The modem provides assistance for automatic answer- ing through the Ring signal as follows. Observe the upper right-hand portion of Figure 6. Assume that DTR has recently been asserted to cause exit from the initial conditions. Note that if DTR remains OFF, Ring is ignored. Assume also that RTS andBRTS are OFF and that the mode control lines (MCO-MC4) select a normal modem configuration, not a lbopback mode. Automatic answering is initiated by receipt of a Low level at the Ring input, causing entrance to the autoanswer sequence depicted in Figure 8. The modem outputs silence (0.0 volts) at its Transmitted Carrier (TC) output for a time, ta.2for the V.21 and V.23 modes. TheTD pinis clamped OFF and the RD signal is therefore clamped to a Mark (High) during the autoanswer sequence. Upon completion of the answer tone, CD is released. If the mode lines (MCO-MC4) select a 202 of V.23 mode, the transmit filters are set to the forward channel and the receive filters are set to the back channel during the autoanswer sequence. Atthe end of the autoanswer sequence, areturn is made to point A in the loop at the upper right-hand portion of Figure 6. Note that since the answer flag has been set, the autoanswer sequence cannot be entered again unless DTA is first turned OFF, then ON. At this point the phone line connection has been established and data transmission or reception may begin. The Ring input may be activated from a conditioned DAA Ring indicator output for automatic answering or it may be activated by a switch for manual answering. Tying Ring High will disable the autoanswer function of the modem. 14 Am7910/11INITIAL CONDITIONS: (BACK) ATSLow RELEASE CO SET SWENCE eT GTS Low TDIGNORED COMPLET REMAINING SQUELCH YES, er (MAIN) NO, BATS Low YES BACK CHANNEL DATA TRANSMISSION O9833A-12 Figure 6, Transmit Main Channel State Diagram NO Am7910/11 15DATA TRANSMISSION Full-Duplex Following call establishment, full-duplex data transmis- sion can be started by either the called or calling modem. In other words, if the connection has been established and the modemis looping through point A in Figure 6, it no longer matters which is the called and which is the calling modem. Data transmission is initi- ated by asserting RTS. At this time the TD input will be released and a modulated carrier can appear at the TC output. Following a delay, tacon, CTS will turn ON. At this time, data may be transmitted through the TD input. It is a common protocol for the user to always present a Mark at the TD input before RTS is asserted and during the tron, delay. Data transmission continues until RTS is tuned OFF. Following a short delay, trcorr, CTS turns OFF. As soon as RTS goes OFF, the TD input is ignored and the TC output is set to 0.0 volts (silence). After CTS turns OFF, the state machine returns to point A in Figure 6. 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 baud or on the back channel at 5/75/150 baud. In normal half-dupiex operation a single modemis either transmitting on the main and receiving on the back channel or vice versa. In the modems, control of the transmitter and receiver filters to the proper channel is performed by RTS. When RTS is asserted, the trans- mitter 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 on, BRTS should not be asserted since the transmitter can- not be used for the back channel. When RTSis OFF 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. lf RTS andBRTS are asserted simultaneously, RTS will take precedence. However, if BRTS is asserted before RTS and the back channel data transmission sequence has been entered (Figure 7), RTS will be ignored until BRTS is turned OFF. The state machine sequences for main and back chan- nel transmission differ slightly and are depicted in Figures 6-9. Assume the state machine is idling through point A in Figure 6. Main 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 RD sig- nal is clamped to a Mark, and the CD signal is clamped OFF. The TD input is released and a carrier appears at the TC output which follows the Mark/Space applied to TD. RTS turning ON initiates a delay, trcon, at the end of which the CTS output goes Low. When CTS goes Low, data may be transmitted through input TD. Data trans- mission continues until RTS is turned OFF. At this time several events are initiated. First a delay (trcorr) iS initi- ated at the end of which CTS turns OFF. The TD input is ignored as soon as RTS goes OFF. If a 202 mode or V.23 soft turn-off mode is selected, a soft turn-off tone appears at the TC output for a time (tsro) followed by si- lence (0.0 volts). For both 202 and V.23 modes a squelch period, tso, is initiated when RTS goes OFF. During this period the CD output is clamped OFF, forc- ing the RD output to a Mark condition. The squelch period begins as soon as RTS goes OFF and thus over- Japs both tacore and tsro. At the end of the squelch period, the state machine retums to the idle loop at point A in Figure 6. The reasons for squelch and soft-turnoff are as follows: Soft Turn-OffWhen RTS is turned OFF at the endofa message, transients occur which may cause spurious space signals to be received at a remote modem. During soft turn-off the modem transmits a soft carrier fre- quency for a period (tsto) after RTS is turned OFF. This results in a steady Mark on the RD line of the remote modem. SqueichThe local receiver must be turned OFF atter RTS is OFF, until the start of carrier detect, so that line transients are not demodulated. The process of dis- abling the receiver after RTS is turned OFF is called squelching. Back Channel This transmission sequence, shown in Figure 7, is entered if a 202 or V.23 mode is selected. RTS is OFF, and BRTS is asserted. The BCD output is forced OFF and the BRD output is clamped to a Mark. The BTD input is released and a carrier appears at the TC output which follows the Mark/Space applied to BD. Turning on BRTS initiates a delay (tscroy) at the end of which the BRTS output goes Low. When BRTS goes Low data may be transmitted through input BTD. Data transmis- sion continues untilIBRTS is turned OFF. The input BTD is immediately ignored and the TC output is silenced {setto 0.0 volts). Following a short delay (teacorr) the out- put BCTS goes OFF. The signais BCD and BRD are re- leased and the state machine retums to idle at point A of Figure 6. In 202 5-bps back channel mode, BTD should be tied High. ThenBRTS controls the ON/OFF keying modula- tion. When BRTS is Low, 387 Hz appears at the TC output; when BRTS is High, 0 volts appears at TC. 16 Am7910/11RESET SILENCE BTD RELEASED SET SILENCE SET BCTS LOW (at) BACK DATA TRANSMISSION BTD IGNORED SET SILENCE arcore Ho COMPLET! SELBCTS HIGH BEO RELEASED e 09833A-13 Figure 7. Transmit Back Channel State Diagram Am7910/11 17Answer Set Answer Silence 1 t si No Coampiet Yes q Set Answer _Tone Delay CO forced off BCD off Silence 2 'sn2 No Complet Yes Reset Answer Tone Delay Release CD Release BCD Set Silence 04262-10C6 Return Auto Answer toA Figure 8. Autoanswer State Diagram 18 Am7910/11DATA 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 DIR is asserted. It then loops until either CD or BCD occurs. Full-Duplex In full-duplex data reception, CD 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 a time (tcvox) the output CD is turned ON, the RD output is released, and valid data can be obtained at RD. Data is received until the receiver detects loss of carrier for at least a time (tcoorr). At this time the CD output is turned OFF 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 above, when a half-duplex mode has been selected the signal RTS controls whether the main channel is transmitting or receiving. The back channel can do only the opposite fromthe main. If RTS is OFF, thenCD may be activated and the data reception sequence is identicat to that dis- cussed above for full-duplex reception. As long as RTS remains OFF, BCD will never be activated. If RTSis ON, thenTD 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 a time (tacoon) the output BCD is turned ON, the BRD output is released and valid data can be obtained at BRD. Data is received until the receiver detects loss of back channel received signal for at least a time {tecoorr). At this time the BCD output is turned OFF. Data output, BRD, is clamped to a Mark if a V.23 mode or 202 150-bps back channel mode is selected. For 202 5-bps back channel mode, BCD represents the received data. The BRD output can be ig- nored. The state machine returns to the idle loop at point E. Am7910/11 19INITIAL CONDITIONS: E DTA Low YES. ANALOG LOOP BAC NO NO YES CARRIER COMPLETE DETECTED YES NO SET GB Low ANALOG AD RELEASED LOOP MA! NO CARRIER DETECTED, SET BCD LOW BRD RELEASED SET BCD HIGH BCD HIGH BRO - MARK BELL 202 SET BCO HIG RECEIVER MAIN/BACK CHANNEL 09833A-14 Figure 9. Receiver Main/Back Channel State Diagram Am7910/11Table 4. Am7910 Timing Parameters (Refer to Figures 10, 11, 12, and 13 for Timing Diagrams) CCITT Bell Bell CCITT CCITT CCITT CCITT V.23 Bell CCITT 103. 103) V.21 v.21 V.23 v.23 Mode2 Bell 202 V.23 202 Symbol Description Orig Ans Orig Ans Mode1 Mode2 EQ 202 EQ Back Back Units trcon @ Request-to-Send to ms Clear-to-Send ON 208.3 208.3 400 400 208.3 208.3 208.3 183.3 183.3 - - 403% Delay tacorr @) Request-to- Send to Clear-to-Send OFF ms Delay 0.4 0.4 0.4 0.4 0.4 0.4 0.4 04 04 - - +40% tercon @) Back Channel Request-to-Send to Clear-to-Send ON Delay - - - - - - - - - 623 - +0.64% tarcorr @) Back Channel Request-to-Send to Clear-to-Send ms OFF Delay - - - - - - - - - 0.4 - +40% tcpon Carrier Detect 92.106 92.106 301- 301- 114.4- 11.4 11.4- 18 18 - - ms ON Delay 308 308 16.4 16.4 15.4 22 22 teporr @ Carrier Detect 21-31 21-31 21-31 21-31 3.5-9 35-9 95-9 12-1712-17) - ms OFF Delay tecpon Back Channel! Carrier Detect - - - ~ - - - - - 17- 17- ms ON Delay 25 25 tecoorr @ Back Channel Carrier Detect - - - - - - - - - 21- 21- ms OFF Delay 35 35 tar Answer Tone Duration 9 19 - 3.0 3.0 3.0 3.0 19 19 - - sec 40.44% tsa. Silence Interval before sec Transmission 1.3 13 1.9 1.9 1.9 1.9 1.9 1.3 1.3 - +064% te @ Receiver Squelch ms Duration - - - - 156.3 156.3 156.3 156.3 1663 - +3.3% tsto @ Transmitter Soft ms Turn-Off Duration - - - - - - - 24 24 - +2.3% tana Minimum RING Low Duration - 25 - 25 25 25 25 25 25 - - ps Note: @- @ refer to designations on timing diagrams in Figures 10,11, 12, and 13. Am7910/11 21Table 5. Am791t Timing Parameters (Refer to Figures 10, 11, 12, and 13 for Timing Diagrams) Cccimy =cciTr: CCITT Bell Bell Bell Bell CCITT CCITT V.23 V.23 V.23 Bell CCITT 202 202 103 103 )~=V.21 v.21 Mode Mode Mode2 Bell 202 V.23 150 5 Symbol Description Orig Ans Orig Ans 1 2 EQ 202 EQ Back Back Back Units trcon @ Request-to-Send to ms Clear-to-Send ON 25.0 25.0 25.0 25.0 8.0 8.0 8.0 80 BO - - - 40.3% @ Delay trcorr Request-to-Send to Clear-to-Send OFF ms @ Delay 052 052 0.52 0.52 0.52 0.52 052 052 052 - - - +40% tarcon Back Channel Request-to-Send to Clear-to-Send ms ON Delay - - - - - - - - - 6823 823 40.64% teacore Back Channel Clear-to-Send ms OFF Delay - - - - - - - - - 052 052 - +40% teoon @ Carrier Detect ON Delay 10-16 10-16 10-16 10-16 3-5 3-5 36 $35 3-45 - - - ms tcoorr @ Carrier Detect OFF Delay 7-20 7-20 7-20 7-20 2-8.5 2-8.5 2-85 2-85 2-85 - - ms tacpon Back Channel Carrier Detect ON Delay - - - - - - - - - 1820 18-20 3-6 ms tacoorr @ Back Channel Carrier Detect OFF Delay - - - - - - - - 22-35 22-35 8-20 ms ter Answer Tone sec Duration - 19 - 3.0 3.0 3.0 3.0 19 19 - - 40.44% ters Silence Interval sec beforeTransmission - 2.0 _ 2.0 2.0 2.0 2.0 2.0 2.0 - - - 40.64% sec tse Silence after AT - - 75 75 75 75 75 75 - - - 40.69% tsa @ Recsiver Squelch ms Duration - - - - 9.0 9.0 9.0 90 9.0 - - - 43.3% tsto @ Transmitter Soft ms Turn-Off Duration - - - 8.0* 8.0 8.0 8.0 80 - 42.3% trine Minimum RING Low Duration - 25 _ 25 25 25 25 25 25 - - - ys * Soft turn-off tone is generated only for selected V.23 modes. Note: @- @ refer ta designations on timing diagrams in Figures 10,11, 12, and 13. 22 Am7910/41SON|BA JOJ g pUe p SAIqe] Gag eyes 0} Jou s} WeIGEIP Buiwn SiyL,. "0 < Gy 228N eg Aq papiaoud Aejop peuseyxe Ue SI, . gt-veeeso sleuuey yoeg Sdq-g YM Burwi, eyeyspueH 202 eg OL e4nBi4 fe | Oke | fo] 6 @ HOTANDS y vivd | >YHVW dd dog go ois| vivd NIV | WHVW NIV t+ WYVW HOVE - MYVW HOVE ervnsCiH __ yHVN WOWA | ols viva NIV te 94 MOH YVAN | | $19 Slyug 23 Am7910/11Sulu, exeyspUeH EZ"A LLIOD LL eunByy SI-VEEBBO SONIBA 10) PUB p S|GEL 98S a/B9S 0} Jou si WesHeIp Bulwiy siui,, OBL G < Gy Ves eyt Aq papiaaud Agjap jeuaixe UE SIG) . he wa ike! > > @| [ @| & @ ] [ @ HOTaNOS y aua Y viva | HVA yy viva baw au goa a9 viva NIVW prww NIV viva yOva | wHvW|xOvE | ou viva wove | 2uvl vLva NIVW SSS LLL LLL 1 \N vlva yUVA Y Wil ll if, YEG slog sl9 Siua si | ua Am7910/11 24SON(BA JO} G PUB y SB\Qe] Ges ejeds Oo} OU S| WesGelp Buln siq),, 0 < Gy J08n ey Aq pepiaoid Agjep jeweixe ue 61). Buju, exeyspuey sdq ogt Z0z Heg PUE OLS EZ'A ZI esnbI4 ZL-VEESEO Icy IC) o| (ei & Oo 6 Wy viva | Uv Gu Uy viva pruwn as ous Wivd NIV pv Nivi 5D viva ove == | | tavw| ova }-._ ow WIEEYY_ |" WWE. * | wa ( 25 Am7910/11,Hujw, exeyspueH 1Z"A/EO! [leg EL eanByy BONIBA JO] G PUB y SEITE] BBS efeIs oO} JOU SI WesbeIp BuIA si), BL-VEERE6O So @ ro 6) 1iV0 Q3AIZ03Y ad go Y3IWYVO GSAIZ03Y se viva VA ers Ot SS YY viva yHVA WY CMY aL XN si9 sug __| | Am7910/11LOOPBACK Eleven modes exist to allow both analog and digital loopback for each modem specification met by the Am7911 (ten modes for the Am7910). When a loopback mode is selected, the signal processing (filters, etc.) for both the transmitter and receiver is set to process the same channel or frequency band. This allows the ana- log output (TC) and the analog input (RC) to be con- nected for local analog loopback. Alternatively the digi- tal 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. First, autoanswer is dis- abled. Second, if a half-duplex_loopback mode is selected (202 or V.23), the local CD/BCD is not forced OFF when RTS/ BRTS is asserted. The 202 and V.23 main loopback modes allow use in a four-wire configuration at 1200 bps. Four-Wire, Full-Duplex The modem can be configured to work full-duplex over four-wires by selecting one of the loopback modes. The loopback modes allow independent operation of the transmitter and the receiver within the modem. The 202 and V.23 main loopback modes allow full-du- plex communication of up to 1200 bps over four-wires. CLOCK GENERATION Master timing of the modem is provided by either a crys- tal connected to the XTAL: and XTALz pins or an exter- nal clock applied to XTAL. Crystal When a crystal is used it should be connected as shown in Figure 14. 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 derived from one of several crystal-driven baud rate generators. it should be con- nected to XTAL: and XTAL2 must be left floating. The timing parameters required of this clock are shown in Figure 15 and the values are listed in Table 6. Crystal Information (f = 2.4576 MHz) Manufacturer P/N C1 C2 M-Tron MP-2 10 pF 20 pF Monitor Products MM-33 10 pF 20 pF Note: Rise time of Vcc must be greater than 5 ms to ensure proper crystal oscillator start-up. or c EL 247 & XTAL, cLockK)> Ta," N.C. >| 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. Figure 14. Clock Generation Am7910/11 27toy 'o} Vince y \ Vite + tor ton or Figure 15. External Clock Table 6. Clock Parameters Symbol Parameters Min. Typ. Max. Units toy Clock Period 406.86 406.9 406.94 ns ton Clock High Time 165 ns tor Clock Low Time 165 ns tea Clock Rise Time 20 ns ter Clock Fall Time 20 ns Reset Modes Automatic Power-On-Reset in Figure 16 is the recom- mended circuit to initiate the internal reset sequence automatically whenever Vcc is applied. Vcc rise time should be faster than one half the RC time constant. The modem contains a diode to discharge the capacitor when Vcc = 0 V. Reset InputThe modem can be forced into the inter- nal reset sequence by setting Reset Low for at least one clock period. Note that Vcc must be at least +3.5 V for proper reset operation. Between repetitive reset pulses, Reset must be High for at least 1 ps, as shown in Figure 17. Upon device initialization or mode change, DTR must be brought High for a time tusu > 100 ms, as shown in Figure 18. Power Supply For maximum performance, power supply bypassing should be used. Vcc should be decoupled to DGND and Vea to AGND as shown in Figure 19. The 0.01 pF ceramic disc capacitors should be mounted as physi- cally close to the pins as possible. cc Am7910 RESET DGND R 1 MQ (420%) Cc I .047 pF (420%) 09833A-20 Figure 16. Automatic Reset 28 Am7910/11Voc 35V-- + >407ns VILA 09833A-21 Figure 17. Reset Timing Diagrams MoM 7, resneo none tusu 08833A-22 Figure 18. Mode Setup +5 Vde | Voc 0.01 pF TT ~ DGND Gno ~-} Am7910/11 TT AGND 0.01 pF BB -5 Vde 09833A-31 Figure 19. Power-Supply Connections Am7910/11 29ABSOLUTE MAXIMUM RATINGS Storage Temperature ............. -65 to +125C Ambient Temperature with Power Applied Commercial (C) Devices ........... 0 to +70C Industrial (I) Devices ............. 40 to +85C Extended (E) Devices ........... -5 to +125C Vecwith Respect to DGND............ +6V/-4V Ves with Respect to DGND ........... -6V/4+4V All Signal Voltages with Respect tODGND ......... 0.222 eee ee ees 45V Stresses above those listed under ABSOLUTE MAXI- MUM RATINGS may cause permanent device failure. Functionality at or above these limits is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability. OPERATING RANGES Positive Supply Voltage (Vcc) .. ... - +4.75 to +5.25 V Negative Supply Voltage (Ves) ..... 4.75 to -5.25.V Commercial (C) Devices ............. 0 to +70C Industrial (Il) Devices .............. 40 to +85C Extended (E) Devices ............ 55 to +125C Operating ranges define those limits between which the functionality of the device is guaranteed. Am7910/1tDC CHARACTERISTICS (over operating ranges unless otherwise specified) Digital inputs: MCO-MC4, DTA, BRTS, TD, BTD, RTS,RING Digital Outputs: CTS, BCTS, CD, BCD, RD, BRD Parameter Parameter Symbol Descriptions Test Conditions Min. Typ. Max. Unit Vou Output High Voltage lon = 400 mA Ci = 50 pF 2.4 Vv Vor Output Low Voltage lo. = 2mA Cw = 50 pF C,| Devices 0.4 Vv E Devices 0.6 Vv Vin Input High Voltage 2.0 Vee Vv Va Input Low Voltage 0.5 0.8 Vv Vine External Clock Input High (XTAL;) 3.8 Voc v Vite External Clock Input Low (XTAL,) 0.5 0.8 Vv Vir External Reset Input High (Reset) 3.8 Veo Vv Vir External Reset Input Low (Reset) -0.5 0.8 Vv he Digital Input Leakage Current 0.0 < Vin< Veo -10 10 pA fia Reset Input 0.0 < Vin < Veo Leakage Current C,! Devices -0.75 0.75 pA E Devices -1.0 1.0 pA ke Vee Supply Current C Devices 140 mA | Devices 160 mA E Devices 170 mA las Vas Supply Current C Devices 15 mA | Devices 20 mA E Devices 25 mA Cour Output Capacitance f = 1.0 MHz 15 pF Cw Input Capacitance f = 1.0 MHz 15 pF Vee Positive Supply Voltage 4.75 .25 Vv Vas Negative Supply Voltage 4.75 -5.25 Vv AGND, Ground Offset -50 50 mV DGND Am7910/11 31Standard Load Circult Test Point Voc From Re Output lr Under 1950 O +1% Test 48 K41% 09833A-24 Notes: 1. C: = 50 pF including stray and wiring capacitance All diodes are 1N3064 or equivalent All resistors are 1/8 watt Vcc = 5 Volts + 5% POND 32 Am7910/11SWITCHING CHARACTERISTICS over operating ranges Parameter Parameter Symboi Descriptions Min. Typicai Max. Unit Part Transmitter Vie TC Output 0.548 Ves Voltage -3.0 dBm Vices TE DC Offset -100 100 mV Toet Delay from TD to TC Change 8.3 ps face Frequency Accuracy (Except 202) -0.4 0.4 Hz face Frequency Accuracy 202 Mark -1.0 1.0 Hz Receiver Vac RC Input Voltage -1.6 1.6 Vv Rin Input Resistance 50 Kohms Vacos Allowed DC Input Offset -30 +30 mV fro Frequency Deviation Toierance ~-16 16 Hz Vepon Carrier Detect on Level 40.5* dBm 7910 42.0* dBm 7911 Veoorr Carrier Detect off Level 45.0 dBm 7910 47.5* dBm 7911 Vive Carrier Detect Hysteresis 45 dB 7910 5.5* dB 7911 Note: All TC levels are measured using a 600 ohm load. All dBm measurements are referenced to 600 ohm. * nominal spread = +1 dB Out-of-Band energy: See Figure 16 Performance Figure 20 shows a graph of nominal bit error rates forthe various modem types. A flat line condition, back-to-back wire connection, is used to allow easy correlation by users. Am7910/11 33Flat Line Receive Level = -30dBm}:- Gaussian Noise - Room Temperature 10 12 Signal to Noise Ratio (dB) Figure 20. Am7910/11 Nomina! Bit Error Rate 14 16 18 Am7910/11FREQUENCY (kHz) dB* 15 dB/OCTAVE * This is the Output Level Relative to the Transmitted Signal ** This Chart Applies to Ail Frequencies Other than the Oscillator and its Harmonics -60 0.01 0.1 6.2 1.0 10.0 100 Figure 21. Out-of-Band Transmitter Energy APPLICATIONS The Am7910 and Am7911 allow designs for many FSK applications. The AMD Modem Technical Manual goes into details on many different applications with specific examples. The Modem Technical Manual also gives additional information on the hybrid (Figure 19) and line interface design (Figure 20) (Order No. 09560C). Stand-Alone Modem A stand-alone modem can be configured using the Am7910/11 RS-232/V.24 line drivers and receiver, a phone line interface (DAA or acoustic coupler), and a two-to-four wire hybrid. A modem suitable for connec- tion to a serial computer port is shown in Figure 17. Since the Am7910/11 interfaces only to TTL-level de- vices, RS-232/V.24 line drivers and receivers are re- quired for connection to devices accepting standard RS-232/V.24 voltage levels. Automatic answering of the telephone can be assisted by the Am7910/11 in this arrangement. Once the DAA has been placed in the off-hook state by the user's inter- face, the DAAwill assert RING onthe Am7910/11. This answer tone conforms to the Bell and CCITT V.25 stan- dards on duration, frequency, and amplitude. Tying RING High onthe Am7910/11 disables the generation of the answer tone. System Configurations Since the Am7910 and Am7911 are multi-mode modems, one basic modem design can be used to meet both North American and International market require- ments. Under the control of a microcontroller such as the Am8031/51, the modems can be easily recontigured from one mode to another with no hardware changes. Both modems are autoanswer, but to implement autodial an external DTMF generator is required. A sister chip, the Am79101 includes full autodial support with integral OTMF generation, Call Progress Tone Detection, and Answer Tone Detection. The four- to two- wire hybrid function is also on-chip. In contrast to the standard two-wire dial-up or switched network, most dedicated networks use four-wire leased lines. The Am7910 and Am7911 can be easily config- ured for four-wire full-duplex operation at 1200 bps. The Am7911 is the recommended modem for this applica- tion due to the short RTS/CTS delay timing which allows multidrop operation on four-wires. Figure 18 shows an example of the Am7910/7911 under the control of an Am8051; the modem is placed in analog loopback to allow 1200 bps full-duplex operation. The line interface typically comprises two line isolation transformers with a simple line impedance matching network and appropriate protective diodes. Am7910/11 3520 RS232/V24 Receivers an AAIAAAA UVV VY Ue RS232/V24 Receivers BTD Data DT Tip [9 vo TI DR Phone qT = DAA Line TXIN Dupl Ringing Ring7o uplexer (Hybrid) RC le RxOUT Alp {| > WV -5V yy Cy" XTAL, T rT u 2.4576MHz [3 XTAL, Co* CAP, OL 1 2000pF 100 2 7910 910 2 7911 CAP, +5V 5V 1 +5V _ Power .047nF Vv Supply RESET 1k Io FING Voc -5V *Value as recommended by crystal manufacturer. \ss 45V **RC is AC coupled to the hybrid and DC coupled DGND to ground (C = 0.33yF, R = 100kQ). V ALB = Analog Loopback Local Copy AGND i. 04811-32B Figure 22. Stand-Alone 7910/11 Application Am7910/1110pF 2.4576MHz 20pF 1 Int | 10F { Am7910/14 6002 pay F XTALI XTAL2 Ring P1.0 TX ik x Mca p11 Am8051 iL 3 [+ P12 1 1.4 Port 0 RX iI z gota, MCo |* P15 == =H Capi RTS * bys a P1.7 2000 pF +7 RD P3.0 100 Q(7910) , 910 2(7911) CAP2 TD P3.1 w P3.2 Address/ +5V CTs P3.4 Data Bus 1MQ cD P3.5 RESET 0.047 uF v INT 09560A-3.17 Figure 23. 1200 bps Four-Wire Full-Duplex Circuit R, = 600 ohm Rz = 22 kohm Rs = 220 kohm R, =2.5 kohm Rs =22 kohm R, = 22 kohm R; =300 ohm Rio Co Ry = 1550 ohm AW_} R, =39 kohm Rio = 11 kohm Rg Ri: = 100 kohm nn CG, =2.2 pF R C, = 0.08 pF AAA Cy = 0.0022 pF Cy Ry Rg > C, = 0.033 pF Input From TC >_ } WN AW > C4 Output to RC 4 - WA Output t R Rs 3 Ry Phone. 3 Rg , Ray Re Line 1 TF 3 = = => isolation Typical Transformer Load Impedance 04811-30B Figure 24, Four-to-Two Wire Active Hybrid Circuit Am7910/11 37o Oo TC AM7910/11 Hybrid Phone Line RC o Oo Ye T ' Hook ' Relay a On Hook Input Ring = Indicator Circuit Ring Output O9560B-6.2 Figure 25. Am 7910/11 Phone Line Circuit Am7910/11PHYSICAL DIMENSIONS PD 028 1.440 | - 7,460 | ooo te een en ee oe a 530 580 4 Lo oy Ld Ls SSeS ooo aca eS ee ~ _ a 045 o a OBE 110 005 MIN 580. .015 .620 .060 > 140 o 225 ' 15 .008 vy - 2015 .125 014 .160 .023 06842B CD 028 ae 1,435 r 1.490 - 098 555 605 1 j _ _. LL 050 .100 O65 BSC .005. MIN 590 01 615 160 4 ,060 008 169 oO O12 cy t ft 15 725 a 150 160 je \ qa __ 015 bug__-700 __ | 022 MAX 06837C Am7910/11PHYSICAL DIMENSIONS (continued) PL 028 042 048 .050 REF pe! |< | oomomor 0 1 al q al C a 485 ws | 4 D __ o96 aso 0 1] 932 ac6 |(O a 456 | q Nj \ ____ \ DIWLILITITMLy 450 456 120 485 162, tor mt 180 495 06751E 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 assumes no responsibility for the use of any circuits described herein. Advanced Micro Devices, Inc. 901 Thompson Place, P.O. Box 3453, Sunnyvale, CA 94088, USA 1989 Advanced Micro Devices, Inc. | Tel: (408) 732-2400 TWX: 910-339-9280 TELEX: 34-6306 TOLL FREE: (800) 538-8450 Si6/89 i APPLICATIONS HOTLINE TOLL FREE: (800) 222-9323 + (408) 749-5703 o2e7 25 a _ 4