🚀 go-pugleaf

   We are experiencing a problem when communicating with a Zenith Z-248 to
   a controller that is used to run a stock carousel.  Both COM1 and COM2
   intermittently fail to receive messages returned by the controller even
   though the messages can be seen on a data monitor as being accurate.
   The problem will occur on one port, both ports, or neither port at any
   given time.

   TROUBLESHOOTING:

   So far the following trouble shooting measures have been tried:

   1.   Cable configuration.  While only using three wires--ground,
        transmit and receive--we tried various jumpers at each end between
        RTS, CTS, CD, etc.  Final configuration on the host was DSR to DCD
        to DTR and RTS to CTS.  On the controller side we had RTS to CTS
        and DSR to DTR.  (Final configuration was the one recommended by
        the manufacturer.)

   2.   Baud rate.  We tried slower baud rates as low as 300.

   3.   Parity combinations.  We went from odd to even.

   4.   Clock rate.  Changed the clock rates on the CPU to slow, smart, and
        fast.

   5.   Timing constant in software.  Changed to conform with real
        milliseconds vs. internal clock time.

   6.   Interrupt processing.  Tried interrupt processing as suggested by
        Zenith and the carousel controller manufacturer.

   7.   Hardware changes.  Both the 8MHZ Z-248 (Government Model) and the
        12MHZ commercial model have been used.  I/O and communications
        cards have been changed multiple times.

   When the problem occurs, we are sending valid data to the controller and
   the controller sends valid data back (according to the data monitor);
   however, our program would never receive the data.  The problem occurs
   so intermittently that we have not been able to find a correlation
   between its occurrence and any given sequence of events.

   We don't feel that this is a problem in the program since the majority 
   of the time, it runs properly.  When it fails, switching to the other
   port would allow us to continue if that port was working at the time.

   None of the above troubleshooting actions caused change in the symptom.

   Any ideas and/or help are appreciated.



-- 
John Burton Stroupe  (DEFENSE DEPOT MEMPHIS TN)     | Remember: No good |
2163 Airways BLVD   			            | deed ever goes    |
Memphis Tn  38114     901-775-6953   AV 683-6953    | unpunished.       |
   osu-cis!dsac!ddmtg1!bstroupe or bstroupe@ddmt.dla.mil