






                                                               COURIER  HST

                                                                 APPENDIX B
                                                       SUMMARIES AND TABLES


          CONTENTS

          B-1  The RS-232C Interface, with Pin Definitions

          B-2  Front End Indicators

          B-3  DIP Switch Summary

          B-4  Default Settings

          B-5  S-Register Summary

          B-6  ASCII Chart



































                                                                        B-1











                                                               COURIER  HST

          APPENDIX B-1
          THE RS-232C INTERFACE, WITH PIN DEFINITIONS
          

          DESCRIPTION

          The RS-232C interface (often referred to without the C) is a
          standard developed by the Electronic Industries Association
          (EIA).  It defines the signals and voltages used when data is
          exchanged between a computer or terminal and a modem or serial
          printer.  Data is transmitted between the devices via a cable
          with 25-pin, 9-pin or custom-built connectors.

          PIN ASSIGNMENTS

          The entire standard covers many more functions than are used in
          most data communications applications.  Pin assignments are
          factory set in the Courier 2400e to match the standard DB-25
          assignments in the following table.  DB-9 connectors at the
          computer/terminal end of the cable should be wired to reflect the
          pin assingments in the DB-9 column.

                         RS-232C INTERFACE PIN DEFINITIONS
                              
             DB-25   DB-9 Circuit    Function            Signal Flow       
               2      3      BA      Transmitted Data    Terminal    Modem
               3      2      BB      Received Data       Terminal    Modem
               4      7      CA      Request to Send     Terminal    Modem
               5      8      CB      Clear to Send       Terminal    Modem
          
               6      6      CC      Data Set Ready      Terminal    Modem
               7      5      AB      Signal Ground       Terminal    Modem
               8      1      CF      Carrier Detect      Terminal    Modem
               12     --    SCF      Speed Indicate      Terminal    Modem
          
               20     4      CD      Data Terminal Ready Terminal    Modem
               22     9      CE      Ring Indicate       Terminal    Modem
          
          MINIMUM REQUIREMENTS

          Some computer/terminal equipment supports only a few of the RS-
          232C signal functions set in the Courier.  The minimum required
          for the modem to operate are as follows:

             DB-25   DB-9     
              Pin    Pin      Function            
               2      3       Transmitted Data
               3      2       Received Data
               7      5       Signal Ground
               20     4       Data Terminal Ready*
          

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                                                               COURIER  HST

          * Required only if you have set the Data Terminal Ready (DTR)
          Override switch (DIP switch 1) OFF (UP).

          If your computer and software support Clear to Send and you wish
          to use Transmit Data hardware flow control (&H1), Pin 5 (DB-25)
          or Pin 8 (DB-9) is required.  If your computer and software
          support Request to Send and you wish to use Received Data
          hardware flow control (&R2), Pin 4 (DB-25) or Pin 7 (DB-9) is
          required.











































                                                                        B-3











                                                               COURIER  HST

                                                               APPENDIX B-2
                                                       FRONT END INDICATORS


          Symbol    Meaning        Status

            HS      High Speed     9600-bps calls only:  ON during call
                                   progress, after completion of dialing;
                                   OFF during link negotiations at 2400
                                   bps; ON during connection.  Remains ON
                                   after disconnect until next call is
                                   originated or answered.

                  AA          Auto Answer/   Answer Mode only:  ON when
                your modem is             Answer       in Auto Answer Mode,
                and when answering                          a call; goes
                OFF if the channel is                                 rever
                sed and your modem transmits at                             
                450 bps.  Also goes off when the modem                      
                         originates a call.

            CD     Carrier Detect  ON when the CD override (DIP switch 6)
                                   is ON (DOWN).  ON if DIP switch 6 is UP
                                   and the Courier receives a valid data
                                   signal (carrier) from a remote modem,
                                   indicating that data transmission is
                                   possible.

            OH      Off Hook       ON when the Courier takes control of the
                                   phone line to establish a data link.

            RD      Received Data  Flashes when a data bit is received by
                                   the Courier from the phone line, or when
                                   the modem is sending result codes to the
                                   terminal or computer.

            SD      Send Data      Flashes when a data bit is sent to the
                                   Courier by the terminal or computer.

            TR      Terminal Ready ON when the DTR override (DIP switch 1)
                                   is ON (DOWN).  ON if DIP switch 1 is UP
                                   and the modem receives a Data Terminal
                                   Ready signal from the terminal or
                                   computer via the RS-232C interface.

                  MR          Modem Ready/   ON when the Courier is powered
                on.                       Power        Flashes when the
                modems retrain,                                       inclu
                ding online fallback to 7200 or                             
                4800 bps.


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                                                               COURIER  HST

            RS      Request to     ON when the Courier is powered on if
                       Send        your computer supports RTS on the RS-
                                   232C interface.  OFF if the Courier is
                                   set to &R2 (Received Data hardware flow
                                   control) and the computer lowers RTS.

            CS      Clear to Send  ON until the modem lowers CTS on the RS-
                                   232C interface when Transmit Data
                                   hardware flow control is enabled (&H1,
                                   &H3).

            ARQ     Error Control  Automatic Repeat Request.  ON when the   
                                   Courier is set to &M4 or &M5 and         
                                   successfully connects with another modem
                                   under error control.

            AL      Analog         ON when the modem is in Analog Loopback
                         Loopback       Self-Test Mode.


































                                                                        B-5











                                                               COURIER  HST

          APPENDIX B-3
          DIP SWITCH SUMMARY

          PURPOSE

          The Courier's DIP switches, located at the rear of the modem, are
          for adapting the modem to your equipment and personal
          requirements.  You may also want to experiment and review your
          computer or terminal documentation as necessary.

          Some users are able to move a single switch with a finger tip.
          If this doesn't work for you, use a toothpick or other small
          instrument.

          OPERATIONS

          The DIP switch settings are power-on defaults, read by the
          Courier when it is turned on.  If changed when the modem is on,
          switches 2-5 and 9 require the ATZ (software reset) command to
          initiate the new settings.  The remaining (hardware) switches are
          automatically operative when set UP or DOWN.
          

                 DIP SWITCHES:  UP = OFF (OPEN), DOWN = ON (CLOSED)
                                          
                    Factory
          Switch    Setting   Function
          
            1       DOWN      Data Terminal Ready (DTR) Operations
                              UP   Normal DTR operations; computer must     
                                   provide DTR signal for modem to accept   
                                   commands; dropping DTR terminates a call
                              DOWN DTR always ON (Override)
          
            2       UP        Verbal/Numeric Result Codes
                              UP   Verbal (word) messages
                              DOWN Numeric codes

            3       DOWN      Result Code Display
                              UP   Quiet Mode, no display
                              DOWN Result codes displayed

            4       UP        Command Mode Local Echo
                              UP   Keyboard commands displayed
                              DOWN Display of commands suppressed

            5       DOWN      Auto Answer
                              UP   Modem answers on first ring
                              DOWN Auto Answer suppressed



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                                                               COURIER  HST

            6       DOWN      Carrier Detect (CD) Operations
                              UP   Courier sends CD signal when it connects
                                   with another modem, drops CD on          
                                   disconnect
                              DOWN CD always ON (Override)

            7       UP        Single/Multiple Phone Installation
                              UP   Single phone line connection (RJ11 jack)
                              DOWN Multiple phone installations (RJ12 or    
                                   RJ13 jack); shorts A/A1 to notify other
                                   devices when modem goes off hook and     
                                   line is busy

            8       DOWN      Command Set Recognition
                              UP   Rrecognition disabled (Dumb Mode)
                              DOWN Recognition enabled (Smart Mode)

            9       DOWN      Escape Code (+++) Response
                              UP   Modem hangs up, returns to Command Mode,
                                   sends NO CARRIER result
                              DOWN Modem maintains connection, returns to   
                                   Command Mode, sends OK result

           10       UP        Power-on and ATZ Reset Software Defaults
                              UP   Load from NRAM
                              DOWN Load factory settings from ROM

           Quad     UP        RS-232C Transmitted/Received Data Pin
          Switch                   Assignments
                              UP   Normal assignments: see Appendix B-1
                              DOWN Reverse assignments
          
                              The need to change this setting is rare.
                              Carefully review your computer or terminal
                              documentation before turning this switch ON.

















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                                                               COURIER  HST

          APPENDIX B-4
          DEFAULT SETTINGS

          USER-PROGRAMMABLE DEFAULTS

          You can create your own default configuration and store it in
          nonvolatile random access memory (NRAM) using the &W command
          described in Chapter 5.  Your defaults are then loaded into
          random access memory (RAM) as long as DIP switch 10 is UP when
          you power on the modem.  To view your NRAM settings at any time,
          use the ATI5 command.

          The following table lists the options stored in NRAM.  If DIP
          switch 10 is DOWN at power on, the factory settings listed in the
          table are loaded instead.  The first time the modem is turned on,
          the NRAM settings are the same as the factory settings.




































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          NRAM Options                            Factory Setting     
          
          Normal/error control modes         &M4  Normal/ARQ
          Data compression                   &K1  Auto enable/disable
          Error-control result codes         &A1  Enabled
          Transmit data flow control         &H0  Disabled
          Received data software flow control&I0  Disabled
          Received data hardware flow control&R1  Ignore RTS
          
          DTE rate select                    &B0  Follow connection rate
          Link rate select                   &N0  Variable link operations
          Data Set Ready (DSR) signal        &S0  Override
          
          Stored telephone number            &Z0-3=0   Blank
          Tone/Pulse dialing                 P    Pulse dial
          Online local echo                  F1   Echo OFF
          Speaker control                    M1   ON during dial through    
                                                  connect
          Result code sets                   X1   Extended
          
          Pulse dial make/break ratio        &P0  N. American
          U.S./CCITT answer tone             B1   N. American
          Guard tone                         &G0
          Break handling                     &Y1  Clear buffer, send Break
                                                  immediately
          Word length                        7*
          Parity                             1*   Even parity
          
          *Detected from AT command; determined by terminal/software
          setting.
          
          
          
          NRAM S-Register Option                  Factory Setting
          
          Escape code character, ASCII decimal         S2=43
          Carriage Return character, ASCII decimal     S3=13
          Line Feed character, ASCII decimal           S4=10
          Backspace character, ASCII decimal            S5=8
          Dial wait-time, sec.                          S6=2
          
          Carrier wait-time, sec.                      S7=30
          Dial pause/re-execute time, sec.              S8=2
          Carrier Detect time, 1/10th sec.              S9=6
          Carrier loss wait-time, 1/10th sec.          S10=7
          Touch-Tone duration, spacing, msec.         S11=70
          
          Escape code guard time, 1/50th sec.         S12=50
          Bit-mapped functions, S-Register 13          S13=0
          Bit-mapped functions, S-Register 15          S15=0
          Inactivity/hang up timer, S-register 19      S19=0

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                                                               COURIER  HST

          Received break length, 10-msec. units       S21=10
          
          XON character, ASCII decimal                S22=17
          XOFF character, ASCII decimal               S23=19
          















































                                                                        B-10











                                                               COURIER  HST

          APPENDIX B-5
          S-REGISTER SUMMARY

          USAGE

          The default values are those users typically require.  Change the
          settings with the ATSr=n command, where r is the register and n
          is a decimal value from 0-255:

                    ATS13=8 <Enter>

          The modem does not perform a value-range check.  Some values may
          not work with some equipment, and you'll have to readjust the
          settings.

          To display the contents of a register, use ATSr? as in this
          example:

                    ATS20? <Enter>

          
          Register  Default   Function

            S0 See DIPSets the number of rings on which to answer
                                                 Switch 5   when in Auto
          Answer Mode.  Default = 1, equivalent of DIP switch 5 UP.  S0=0
          or DIP switch 5 DOWN (factory setting) suppresses Auto Answer.
          
            S1                                          0   Counts and
          stores the number of rings from an incoming call.
          
            S2        43      Stores the ASCII decimal code for the escape
          code character.  Default character is "+".  A value of 128-255
          disables the escape code.
          
            S3        13      Stores the ASCII decimal code for the
          Carriage Return character.
          
            S4        10      Stores the ASCII decimal code for the Line
          Feed character.
          
            S5         8      Stores the ASCII decimal code for the
          Backspace character.  A value of 128-255 disables the Backspace
          key's delete function.
          
            S6         2      Sets the number of seconds the modem waits
          before dialing.  If set to X2, X4, X6, or X7, the modem ignores
          this register and dials as soon as it detects a dial tone (fast
          dials).
          


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                                                               COURIER  HST

            S7        30Sets the number of seconds the modem waits  for a
          carrier.  May be set for much longer  duration if, for example,
          the modem is  originating an international connection.
          
            S8         2      Sets the duration, in seconds, for the pause
          (,) option in the Dial command and the pause between command re-
          executions (> and A> commands).
          
            S9         6      Sets the required duration, in tenths of a
          second, of the remote modem's carrier signal before recognition
          by the Courier (Carrier Detect Time).
          
            S10        7      Sets the duration, in tenths of a second,
          that the modem waits after loss of carrier  before hanging up.
          
            S11       70Sets the duration and spacing, in milliseconds, of
          dialed Touch-Tones.
          
            S12       50Sets the duration, in fiftieths of a second, of the
          guard time for the escape code sequence.
          
            S13                                         0   Bit-mapped
          register.  Select the bit(s) you want on, and set S13 to the
          total of the values in the Value column.  For example, ATS13=20
          enables bits 2 (value = 4) and 4 (value = 16).
          
                              Bit  Value  Result
                               0     1    Reset on dropping of DTR
                               1     2    Reverse normal Auto Answer
                                          operation:  on incoming RING,
                                          enter Originate Mode and look for
                                          Answer tone
                               2     4    Disable 250 msec. pause before
                                          result code display
                               3     8    On DTR signal, Auto Dial number
                                          stored in NRAM at position 0
                               4     16   At power on/reset, Auto Dial
                                          number stored in NRAM at position
                                          0
                               5     32   Reserved
                               6     64   Disable MNP Level 3 (used for
                                          testing Level 2)
                               7    128   Watchdog hardware reset, same as
                                          power on (used in factory
                                          testing)
          
            S14                                             Reserved.
          
               S15                                      0   Bit-mapped
          register.  See instructions for S13, above.
          

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                              Bit  Value  Result
                               0     1    Disable the modem's extra high-
                                          frequency equalization if it
                                          causes problems on shorter-link
                                          calls
                               1     2    Disable 7200/4800 bps online
                                          fallback
                               2     4    Disable 450-bps back channel,
                                          force 300-bps back channel
                               3     8    Reset non-ARQ mode Transmit
                                          buffer from 1.5k bytes to 128
                                          bytes*
                               4     16   Disable MNP Level 4;
                                          retransmitting the larger Level 4
                                          data blocks may be a problem if
                                          you expect a great number of
                                          errors during a call
                               5     32   Set Del key to act as Backspace
                                          key; provided for specialized
                                          applications.  May cause software
                                          incompatibility in standard
                                          applications.
                               6     64   Some earlier 2400-bps MNP modems,
                                          not made by USRobotics or
                                          Microcom, were not fully
                                          compatible with the MNP protocol.
                                          If you have difficulty making a
                                          successful 2400-bps MNP
                                          connection with a remote MNP
                                          modem, it may be because of this
                                          incompatibility.  Set S15 to 64
                                          and try again to make the
                                          connection.
                               7    128   Enable Interbridge network
                                          compatibility
          
                              * The default 1.5k byte non-ARQ buffer allows
                              data transfer with X- and YMODEM-type file
                              transfer protocols without using error
                              control.
                              
                              The 128-byte option allows remote users with
                              slower modems to stop data you're
                              transmitting from scrolling off their
                              screens.  When remote users send your
                              computer an XOFF (Ctrl-S) and you stop
                              transmitting, the data in transit from your
                              modem's buffer doesn't exceed the size of
                              their screen.
          


                                                                        B-13











                                                               COURIER  HST

          S16        0                                      Modem self-
          test.  See Appendix E-6 for test procedures.
          
                                 0  Data Mode (no testing)
                                 1  Analog Loopback
                                 2  Dial Test
                                 4  Test Pattern
                                 5  Analog Loopback with Test Pattern
                                 
            S17                                         0   Stores the
          reason for a received ARQ Link Disconnect. May be requested by
          Technical Support if you're having a problem connecting in ARQ
          mode with another ARQ-mode modem. At ATS17?, the modem returns
          one of the following codes.
          
                               1   Received data unit other than link
                                   request
                               2   Incompatible protocol level (3, 2, 1)
                               3   Unknown parameters in link request
                               4   Remote modem retry timeout (Max. 12
                                   tries)
                               5   Inactivity timeout (See S19)
                               6   Destination user not found
                              254  Peer protocol error
                              255  User-initiated disconnect
          
            S18                                             Reserved.
          
            S19                                         0   Sets the
          duration, in minutes, for the Inactivity Timer.  The timer is
          activated when there is no activity on the phone line.  At the
          timeout the Courier hangs up.
          
               S20                                      0   Stores the
          reason for the NO CARRIER result code.  At ATS20? the modem
          returns one of the following codes:
          
                               0   Key press abort
                               1   DTR dropped
                               2   Escape code (+++) issued
                               3   Loss of Carrier
                               4   Inactivity timeout
                               5   Automatic hangup with ARQ
                                   incompatibility (&M5 Mode)
                               6   ARQ Retry timeout (Max. 12 tries)
                               7   ARQ Received Link Disconnect (See S17)
          
            S21                                        10   Sets, in 10-
          millisecond units, the length of Breaks sent from the modem to
          the local terminal.


                                                                        B-14











                                                               COURIER  HST

            S22                                        17   Stores the
          ASCII decimal code for the XON character.
          
            S23                                        19   Stores the
          ASCII decimal code for the XOFF character.















































                                                                        B-15











                                                               COURIER  HST

          APPENDIX B-6
          ASCII CHART
          

















































                                                                        B-16




