SPORTSTER 14,400
                                       APPENDIX F.  MODEM TESTING
                                                                 
      
      Modem testing is available with the &T
      command and Register S16 (Dial test).
      All loopback testing conforms to CCITT
      Recommendation V.54.
      NOTE:  Only one test can be performed at
      a given time.  If you send a test
      command while the modem is in test mode,
      you'll receive an ERROR message.
      
TESTING WITH &T

      The tests supported through the &T
      command include analog loopback, digital
      loopback and remote digital loopback.
      You can key in your own data during
      testing, or use the modem's internal
      test pattern and error detector.
      In all cases, disable error control
      before testing.  If the modem is
      detecting errors and retransmitting the
      affected data, your test results will be
      invalid.
      
Ending a Test_&T0, S18

      Issuing the &T0 command terminates a
      test.  Alternatively, set Register S18
      to a specified number of seconds, for
      example, S18=10.  When the 10 seconds
      are up, the modem automatically ends the
      test and returns to Command mode.  If
      the test was Analog Loopback, the &T0
      command hangs the modem up.  If the test
      was Digital or Remote Digital Loopback,
      issue an ATH command to hang up the
      modem, or an ATZ command to hang up the
      modem and reset it to its defaults.
      NOTE:  If you use the S18 test timer,
      but in the process of testing you issue
      an ATZ command, S18 resets to zero and
      the timer is disabled.  Also, you cannot
      store a value for S18 in nonvolatile mem
      ory:  its power-on and reset default is
      always zero.
Analog Loopback_&T1, &T8

      This test checks the operation of the
      modem's transmitter and receiver.  Data
      flow is shown in Figure F.1.  Modem/DTE
      indicates the modem's interface with
      the computer (Data Terminal Equipment).
                       
                       
  Figure F.1_Data Flow During Analog Loopback
                       
      There are two analog loopback options.
      The first, &T1, involves your typing
      data that you can verify at your screen.
      The second option, &T8, is an internal
      self-test that does not involve the
      keyboard or screen.  It isolates the
      modem from the computer interface to
      give you a more specific result.
   &T1
      1.The modem should be on hook in
         Command mode.  If you wish, set
         Register S18 as a test timer.  For
         example, insert S18=10 in the
         following command string before &T1.
             AT &M0 S18=1 &T1 <Enter>
         The modem disables error control,
         sets the timer, enters analog
         loopback (AL) mode, and sends a
         CONNECT message.
      2.Type recognizable data so that you
         can verify it when it is looped back
         to the screen.
      3.End the test.  If you set S18, the
         modem automatically stops the test at
         the timeout, exits AL mode and
         responds OK.
         If you didn't set Register S18, wait
         one second and type +++ to end the
         test and return the modem to Command
         mode.  When the modem responds OK,
         type AT&T0 to terminate AL mode and
         hang up the modem.  (Typing ATH has
         the same effect.  Typing ATZ also has
         the same effect, but also resets the
         modem and restores your &M default.)
         The modem responds OK.  If the modem
         sends an ERROR message, you have
         issued an invalid command.
      4.If there were no errors, reset the
         modem to &M4, for error control,
         unless you've issued the ATZ reset
         command.
         NOTE:  If the modem is in Online-
         Command mode, that is, still
         connected to a remote modem, and you
         send it an &T1 or &T8 command, it
         drops the call, enters AL mode, sends
         a CONNECT result and waits for
         loopback characters.
   &T8
      This AL option causes the modem to send
      an internal test pattern to its
      transmitter and loop it back to the
      receiver.  An internal error detector
      counts any errors and, when the test is
      ended, sends the number of errors or 000
      (no errors) to the screen.
      Since you don't type anything during
      this test, and the modem does not send
      anything to the screen, this option veri
      fies only the modem.  If there are no
      errors but your problem continues, it
      may be at the computer interface.
      1.The modem should be on hook in
         Command mode.  If you wish, set
         Register S18 as a test timer.  For
         example, insert S18=10 in the
         following command string before &T8.
             AT &M0 S18=10 &T8 <Enter>
         The modem disables error control,
         sets the timer and enters AL mode.
         The modem sends its internal test pat
         tern to the transmitter, and loops
         the pattern back to the receiver.
         You will not see any data on your
         screen.
      2.End the test.  If you set S18, the
         modem automatically stops the test at
         the timeout.  If you didn't set
         Register S18, type AT&T0 to end the
         test.  Or use ATH or the command that
         resets the modem, ATZ.  Both of the
         latter end the test and hang up the
         modem.
         When the modem hangs up it returns a
         three-digit code, followed by OK.  A
         code of 000 indicates no errors were
         found.  A code of 255 indicates 255
         or more errors.  An ERROR message
         indicates that you issued an invalid
         command.
      3.If there were no errors, reset the
         modem to &M4 for error control unless
         you issued the ATZ command.
         
&T2

      This option is reserved.
      
Digital Loopback_&T3

      If your modem has passed the AL test,
      this test can help you locate a problem
      with a remote modem or the telephone
      channel.  Figure F.2 shows the data
      flow during Digital Loopback (DL)
      testing.  Modem/DTE indicates the
      modem's interface with the computer
      (Data Terminal Equipment).
                       
                       
 Figure F.2_Data Flow During Digital Loopback
                       
      1.Set the modem to &M0, to disable
         error control.  Establish a
         connection with the remote modem.
      2.Bring the modem back to Online-
         Command mode with the +++ escape
         code.  Then send it the AT&T3
         command.  The modem enters DL mode.
      3.The remote user should type a short
         message.  It will be looped back by
         your modem's transmitter for
         verification on the remote screen.
         You will not see the message or any
         other data.
      4.When the remote user has completed
         the test,  issue the AT&T0 command to
         end the test.  If you wish, return
         the modem online (ATO) to resume data
         mode.  Or type either ATH or the
         command that resets the modem, ATZ.
         The latter two commands end the test
         and hang up the modem.  The modem
         responds OK.  If the modem sends an
         ERROR message, you have issued an
         invalid command.
         
&T4, &T5

      The &T4 option causes the modem to grant
      a remote modem's request for a Remote
      Digital Loopback test.
      The &T5 option cancels &T4, and the
      modem fails to recognize such a request.
      This is the default so that your modem
      isn't subject to another user calling
      and tying up your modem without your
      permission.
      
Remote Digital Loopback_&T6, &T7

      This test, like the local digital
      loopback test, verifies the condition
      of both modems and the phone link.
      Data flow is shown in Figure F.3.
      Modem/DTE indicates the modem's
      interface with the computer (Data
      Terminal Equipment).
                       
                       
                       
  Figure F.3_Data Flow During Remote Digital
                   Loopback
                       
      The request for and granting of Remote
      Digital Loopback testing requires that
      both modems use CCITT V.54 standard
      signaling.  The test must be performed
      at 2400 or 1200 bps.  If the remote mo
      dem does not have the capability or is
      not set to respond, you will get an
      ERROR result code.
      As with Analog Loopback, there are two
      Remote Digital Loopback options.  If you
      select &T6, you send keyboard data to
      the modem and verify it when it is
      returned over the phone lines and to
      your screen.  If you select &T7, the
      modem sends its internal test pattern
      and returns an error count to your
      screen.
   &T6
      1.Set your software to 2400 or 1200
         bps.  Set the modem to &M0.  If you
         wish, set the S18 timer.
         Establish a connection with the
         remote modem.  If you haven't already
         done so, arrange with the remote user
         to cooperate with your testing.  The
         remote user should set his or her
         modem to acknowledge the RDL request,
         for example, AT&T4.
      2.Bring the modem back to Online-
         Command mode with the +++ escape
         code.  Send it the AT&T6 command.
         The modem enters RDL mode.
      3.Type a short message.  It will be
         looped back to your modem by the
         remote modem and to your screen for
         verification.  (The remote user will
         not see your data.)
      4.End the test.  If you set Register
         S18 the modem automatically ends the
         test when the test timeout is
         reached.  If you didn't set S18, type
         AT&T0 to end the test.  If you wish,
         return the modem online (ATO) to
         resume data mode.  Or send either ATH
         or the command that resets the modem,
         ATZ.  The latter two commands end the
         test and hang up the modem.  The
         modem responds OK.  If you issue an
         invalid command, the modem sends an
         ERROR message.
         Data errors indicate a problem with
         the remote modem or the phone link.
         If you have not performed analog loop
         back testing with your modem, the
         problem may also lie with your modem.
      5.Reset the modem to &M4 unless you
         used the reset command, ATZ.
   &T7
      This test option causes the modem to
      send an internal test pattern through
      the Remote Digital Loopback.  An
      internal error detector counts any
      errors and, when the test is ended,
      sends the number of errors or 000 (no
      errors) to the screen.
      You don't need to type anything during
      this test.  The modem sends only its
      final error count to your screen.
      1.Set your software to 2400 or 1200
         bps.  Set the modem to &M0.  If you
         wish, set the S18 timer.
         Establish a connection with the
         remote modem.  If you haven't already
         done so, arrange with the remote user
         to cooperate with your testing.  The
         remote user should set his or her
         modem to acknowledge the RDL request,
         for example, AT&T4.
      2.Bring the modem back to Online-
         Command mode with the +++ escape
         code.  Then send it the AT&T7
         command.  The modem enters RDL mode.
         The modem sends its internal test
         pattern to the remote modem, which
         loops it back to your modem.  You
         will not see the data on your screen.
      3.End the test.  If you set S18, the
         modem automatically stops the test
         when the timer times out.  If you
         didn't set Register S18, type AT&T0
         to end the test.  After you view the
         test results (next paragraph), return
         the modem online if you wish (ATO)
         and resume data mode.  Or send either
         ATH or the command that resets the
         modem, ATZ.  The latter two commands
         end the test and hang up the modem.
         When you terminate the test, the
         modem returns a three-digit code,
         followed by OK.  A code of 000
         indicates no errors were found.  A
         code of 255 indicates 255 or more
         errors.  If you issue an invalid
         command, the modem sends an ERROR
         message.
         If you've performed an Analog
         Loopback and know your modem is
         working properly, errors indicate a
         problem with either the phone
         connection or the remote modem.
      4.Reset the modem to &M4 unless you've
         sent it the ATZ reset command.
         
DIAL TEST_S16=2

      The Dial test is used for factory-
      testing the frequencies of Touch-Tone
      values.  When S-Register 16 is set to 2
      and a single Touch-Tone is dialed (for
      example, ATD7 <Enter>), the modem con
      tinues to transmit that tone until you
      press the Enter key again.

