PRELIMINARY DATA (Revised)
    
    DtSnNCTIYE CHARACTERISTtCS
    
    Complete FSK MODEM in a 28-pin packego - jusl add
    line intarlace
    Compabble w~th Bell 10311131109 Bell 202 CCITT V.21
    CCITT V.23 speciticabons
    No extemal hltering required
    All digital signal processing digital hilers and ADC/DAC
    indudAd on-chip
    Ineludes essenbal RS 232/CClTT V.24 har dshake
    signals
    Auto~answer capability
    Local cc~py/tesl modes
    1200 bps tull duplex on 4-wire line
    Pin-programmable mode section
    
                 FIgure 1. Connectlon Diegnm
    
          ú"
          R5
         ~r   HD
         v_
         ae   nALd~
       CA#,   "AL,
       CA#1   DG - 7
         TC   ~
      AG.10   ~e,
         TO   ~i
    
        ~E,   li~
        R~E   U'D
    
    GENERAL DESCRIPTION
    
    -
    
    -
    
                            ~ ,.
                             D '
    
    Am7910
      FSK MODEM
      WORLD CHIP'-
      AdvancedMicroDevices
      3
    
    Tha Am7910 is a singl~chip asynchrocous Frequency
    Shih Keying (FSK) vdc-~band modern. It is pin seleclable
    Tor baud rates d 300. 600 or 1200 bits per serx~nd er d is
    compatibl* TAnth tho applicable Bell and CCITT recon~-
    mended standards lar 103/113/108 202 V.21 and V~23 type
    moderns. F've mode contrd hnes seTect a desired modem
    r onfiguration.
    
    Digital signal processsing lechniques are empioyed in the
    Am7910 to pertorrn alt myor tunchons such as m~xtulation
    demodulation and tiltering. The Am7910 contains on-chip
    anabg-to4ighal and digital-to-analog convener cirrults to
    minimize the extemal oomponents in a system This device
    includes ~ essenbal RS-2321CCITT V.24 terminal control
    signals with TTL lavels.
    
    Clocking Can be generated by attaching a crystal to drive the
    intemal crystal oscillator or by appPying an extemal cinck
    signal.
    
    A data access arrangement (OM) or acoustic coupter must
    provKde the phone line intertace extemally.
    
    The Am7910 is tabricated usin4 N<hannel MOS technd-
    ogy in a 26-pin package. All the digital input and output
    signals (extspt the extemal ciock signal) are TTL compat-
    ible. Power suWly requirements are ~ 5 volts.
    
    O1Z¯C ~

    





    
    Figure 2. Am7910 Block Dlagram
    
           t. ~AW
           rRA~saTlrTED~o  ~rR~sÄmTte  _    a    O TRa~sulrTEo ~NV\_
    
    8 ACK
    
    c&, "r
    
          ~_CA.' O
    
    ~ECElVED O
    
    _~...,. ~_~ - A.
    
                      I TAL ,/CLK      ~_
    
    ~ 1At,
    
    "A~
    
       aEcErvE.~' DA'&
              _ BAC K
    
           " O QE0UESI I0 SE - D
           t, O CkEAR TO SE - D   ~A'N
           O tARRtER OEt1C!
           0 ~tOuœIt to St~D
    
     --     O CLtAn ro SEh10 aACK
            O CARR.ER D6TECT
            (3 RINC
            - - O RESEI
    
    O_o ú ~v ~CC
    O ~ o - ~v V~
    ~CNO
    O DCi ~ D
    
    01 23&~:-2
    
    n,
    ~C
    
                              -
                             ~0
                             CO
                             C~
    
    INTERFACE SIGNAL DESCRIPTION
    
    UICUMC4 tCONTROL INPUTS)
    
    These rive inputS select one ol th~rly~lavo modem conhgurat~ons
    accord,ng IO the Beil or CCITT spec~tlcat~ons l~sted in Tabie 1.
    Onty 19 ot these 32 modes are aelually available to the user
    
    Modes 0-8 a~e the normal operat,on modes The 1200 Baud
    modes cen t~e selecied with or wilhoul a comprom~se equalizer
    
    Modes 16 25 permii loop back ot the Am7910 Iransm~ner and
    rece~ver. No ~nternal conneclion i5 made. The user musl
    erlernally connecl the TRANSMITTED CARRIER pin (F.gure 3)
    to the RECEIVED CARRIER pin it analog loopback is required.
    For digital bopback external conneetion o/ RECEIVED DATA
    and TRAr4SMITTED DATA is required. Whenever a rnode in Ihis
    group is selecied. the eHect is lo set all transmil and receive
    fillers lo the same channel irequency band so that loopback con
    be performed.
    
    Modes 9-15 and 26-31 are reserved and shouid nol be used
    
    DATA TERN1INAL READY (DTR)
    
    A LOW kvel on this input indicates the dala terminal desires to
    send and'ol rece~ve dala via the rnodern. This signal is galed with
    all other TTL inputs and outputs so Ihat a bw level enables all
    these signals as well as the intemal control logic to lunclion A
    HIGH lovel d~sabies all TTL UO pins and the internal logic.
    
    RECtUEST TO SEND (RTS}
    
    A LOW level on this inpul Instructs lhe modem to enter I~ansmit

    





    mode. This inpul must remain LOW tor the duration d data
    transmission. The signal has no ellect it DATA TERMINAL
    READY is HIGH (disablect) A HIGH bvel on Ihis input turns oH
    the transminer.
    
    CLEAR TO SEND {CTS)
    
    This output goes LOW at the end ol a delay initialed when
    REOUEST TO SENCI goes LOW. Actual data lo be transmitted
    shouid not be presented to the TRANSh'tlTTED DATA input until a
    LOW is indicated on the CLEAR TO SEND output. Normally the
    user shouid force the TD input HIGH whenever CTS is oft (HIGH).
    _his dgna' never goes LOW as long as DTR is Ht<;R (disabied).
    CLEAR TO SEND goes HIGH at the end ot a detay initiated when
    REQUEST TO SEND t'øes HIGH
    
    _ _
    CARRIER DETECT {CD)
    
    A LOW on this output indicates that a valid carrier signal is
    presenl at the receiYer and has been present lor at least a lime,
    tCDoN' where tCDoN depends upon the selected modem con-
    tiguralion (Table 2). A HIGH on this outpul signihes thal no valid
    carrier is being received and has not been received for a lime,
    tCDoFF. CARRIER DEtECT remains HIGH when DTR is HIGH.
    Values tor ~=N and tC~F are conliguration dependent and
    are listed in Table 2.
    
    TRAN5hIITTED t)ATA (TD)
    
    Data bits lo be transmined are presented on this input serially;
    HIGH (mark) conesponds to bgic 1 and LOW (space) cone-
    sponds to bgic 0 This data delermines which trequeney a~
    paars at any instant al the TRANSMITT!ED CARRIER output pin
    (Table 2). No s~gnal appaars al me TRAlqSMITTED CARRIER
    output unless DTR is LOW and h~ is LOW.
    
    RECEIVED DATA (RD)
    
    Dala bits rJemodulated trorri the flECEIVED CARRIER input
    are avallAbb senally al this ou~ut; HIGH (mark) indic~tes b~ic
    1 and LOW (space) indicates logic 0. Under the tollowing
    condiNons this oulput Is torrod to bgic 1 because the dala may
    be ~nwalid:
    
    1. When CARRIER DETECT is HIGH
    
  2 During the internal squelch delay al hall-duplex line lurn
    around 1202/V.23 martes only)
    
  3. Dur~nrg soh carrier turnott at hall-duplex lene lurn sround
    (202 mo only)
    
    4. When DTR is HIGH
    
    5. When RTS ON and BRTS OFF in V 23~202 modes ooly
    6. During auto-answer sequence
    
    DACK FtEaUEST TO SEND (BRTS)
    
    Since the 1200 bps modem contigural~ons, Bell 202 and CCITT
    V 23, permit ooly halt doplex operation over two-wire llnes, a lo~
    baud rale "backward" channel is provided lor Iransmission trom
    the main channel recelver lo Ihe main channel lransmitter. This
    inpul signal (BRTS) is equivelent lo REOUEST TO SEND for Ihe
    main channel. except il belongs to the bachward channel Note
    that since the Am7910 contains a single transmitter, R~TS and
    BRTS shouid not be assened simultaneously. BRTS is mean-
    inglul ooly when a 202 or V.23 mone is selecied by MCo-MC4 In
    all other modes il is ignored.
    
    For V.23 mode the t~equency appearing Al the transmitled
    carrier (TC) oulput pin is determ~ned by a MARK or SPACE at
    the back transmitted data (BTD) input (Table 2).
    
    For 202 mode a Irequency ol 387Hz ap,oears at TC when BRTS
    is LOW and DTD is HIGH. No energy (0.0 volts) appears al TC
    when BRTS is HIGH. BTD shouid be f~xed HIGH /or 202 back
    channel transmission. The signal, BRTS, then is equivelent to
    the signal, Secondary Request-to-Send, for 202 S''T rnodems,
    or Supervisory Transmitted Oata tor 202 C/D modems.
    
    BACK CLEAR TO SEND (BCTS)
    

    





    This line is cquivelent to CLEAR T0 SEND lor the main channel,
    except it belongs lo the back channel. eCTS is meaningful only
    when a V23 mode is selected by MCo-MC4. This signal is not
    used in Bell 202 back mode.
    
    BACK CARRIER DETECT (BCD)
    
    This line is equivalent to CARRIER DETECT lor the main
    channel, except fl belongs lo the backward channel. DCD is
    meaninglol only when a 202 or V.23 mode is~selected by MCo-
    MC4. For V.23 back channel mode, BCD tums on when either
    the MARK or SPACE trequency sppears with sulticient lovel at
    the reccivad carrier (RC) inpul'
    
    for 202 back channel mode, DCD turns on in response to a
    387Hz tone ol sutlicient level at the RC input. In this case BCD is
    equivalent to the signal, Secondary Rereivad Line Signal De-
    tecior, tor 202 SIT modems, rw Supervisory Received Data tor
    202 CID rnorJems.
    
    BACK TRANSMITTED DATA (eTD)
    
    This line is equivalenl lo TRANSMITTED DATA tor the mAin
    channel, except it belongs to lhe back channel. BTD is mean.
    inglul ooly when a 202 or V~23 rnode is selr.~cied by MC~MC4.
    For 202 back transmission ot onlott keying, BTD shouid be fixed
    at a HIGH level.
    
    aACK RECEIVED DATA (eRD)
    
    This line is equivelent to RECEIVED DATA (excepl clemping) lor
    Ihe main channel, except n belongs io ihe back channel. E3RD is
    meaninglul only when a V.23 mode is selected by MCo-MC4.
    Under the tdiowing conddions this output is torced HIGH:
    
    1. BRD HIGH
    2. DTR HIGH
    3. V.21003rnode
    4. During aut~answer
    5. When BRTS ON and FlTS OFF in V.23 modes ooly