SETTING UP THE MULTITECH 224E FOR HARDWARE FLOW CONTROL
      
      
      With the  advent of  modems using  hardware based  error  correction
      (such as  the  Microcom  Networking  Protocol,  MNP),  several  file
      transfer protocols  making use  of this have emerged, such as IModem
      and YModemG.   These  protocols depend on the modems to handle error
      correction, and  depend on CTS/RTS flow control between the computer
      and modem to ensure that no data overruns occur.
      
      The MultiTech  224E is one of the most popular 2400 baud modems that
      incorporates MNP  error correction  into its circuitry.  Setting the
      various hardware  and software  parameters to enable MNP and CTS/RTS
      flow control  is somewhat  tricky, and  this document is intended to
      simplify that task.
      
      The MT224E  has two  banks of  DIP switches.    One  bank  of  eight
      switches is  accessible via  the rear panel of the modem.  The other
      bank of  four switches  is accessible  only by removing the cover of
      the modem.   The  jumpers are  also accessible  only by removing the
      cover (refer  to your owner's manual for instructions on opening the
      modem and  locating  the  switches  and  jumpers).    The  following
      settings will  enable MNP error correction (providing the modem that
      is called  is so equipped) and CTS/RTS flow control.  They will also
      enable the  full verbose  response set  of the MT224 which will keep
      you apprised  of what the modem is doing, and will wait for dialtone
      before dialing.
      
      The setting  of the  bank of eight switches should be as follows (up
      refers to  the OPEN  position): 1-UP  (DTR  normal),  2-UP  (verbose
      responses), 3-DOWN  (enable command  response), 4-UP (enable command
      echo), 5-UP  (enable autoanswer),  6-UP  (CD  &  DSR  normal),  7-UP
      (single line  RJ11), and 8-DOWN (enable command mode).  All of these
      are the  factory default  settings with  the exception  of switch 1,
      which is reversed.
      
      The setting  of the  bank of  four switches should be as follows (up
      refers to  the OPEN  position): 1-DOWN  (CTS normal),  2-UP (Dial-up
      operation), 3-UP (wait for dialtone), and 4-DOWN (asynch operation).
      Switches 2 and 4 are factory default, switches 1 and 3 are reversed.
      
      The jumpers  should be  set as follows: RTS normal (not forced), CTS
      to follow RTS, and DSR to follow CD.
      
      The following software switches should be set (use ATL5 to determine
      your current settings):
      
      V1 - Word responses               Q0 - Result codes on
      E1 - Echo on                      X1 - Extended result codes
      B1 - Wait for dialtone            &E1 - Auto reliable mode
      &E4 - CTS flow control            &E7 - XON/XOFF pass thru on
      &E8 - ENQ/ACK off                 &E10 - Modem flow control off
      &E13 - Pacing on                  &G0 - Guard tone off
      &T5 - Remote loop off             &C1 - Carrier detect normal
      &R1 - CTS forced on               &A0 - Answer back off
      &V1 - CCIT V.22 answer tone       &Q0 - Multimodem responses
      $MB2400 - Set baud rate 2400      $SB2400 - Set port speed 2400
      $BA1 - Baud adjust on             $D0 - DTR dialing off


      &S1 - DSR normal                  &W0 - Store parameters
      
      After you  have issued the appropriate commands, issue AT&W0 to save
      these settings.
      
      A few  words of explanation on some of the software switch settings:
      &E1 enables  automatic MNP  error correction  if the  modem you  are
      calling also has MNP enabled.  &E4 enables the CTS flow control that
      the new  file transfer  protocols use  to control  data flow between
      your computer  and the modem.  &R1 forces CTS initially high so that
      your communications  program will  know CTS is enabled.  The setting
      of the jumpers and hardware switches ensure that even with &R1, flow
      control will work.
      
      I hope  that this document helps you if you have been having trouble
      setting up  your MultiTech  224E for  reliable  connects  with  flow
      control.   These settings have been tested using Qmodem 3.0 SST with
      both the  IModem and  YModemG protocols  with  artifically  injected
      noise on  the phone  line, and  we have been unable to produce a bad
      file transfer.
      
      S. David Klein
      The Software Society PCBoard
      201-729-7410
      7/1/87