Testing for a bad asynchronous port

UPDATED: August 31, 1999

SUMMARY:

For a possible asynchronous port hardware failure the customer can save time by doing the following diagnosis and reporting the results to Lucent Technical Support.

TESTING:  Test Port with a serial line analyzer (mini-tester)
       Equipment needed:

  • RS-232 DB-25 Serial Line Analyzer (mini-tester) 
  • DB-25 loop back connector-Connect pins like so, 2 - 3, 4 - 5, 8 - 20
  • The serial cable from the PortMaster's (TM) serial port that you wish to test. 

In sequence plug in the mini-tester, then add a loopback connector and then replace the loopback with the signal device. Check the result those listed in table1 below.

Table 1, Normal led patterns with RS-232 tester. 

mini-           with            With modem
tester          loopback        or other
only            connector       DCE device
-----------------------------------------------
 TD - green      TD - green      TD - green     
 RD - off        RD - green      RD - green     
RTS - red       RTS - red       RTS - red       
CTS - off       CTS - red       CTS - red       
DSR - off       DSR - off       DSR - red       
DTR - red       DTR - red       DTR - red       
 CD - off        CD - red        CD - red       

* green is high or +5 volts
* red is low -5 volts 
* off is no light
  • Swap the serial cable-modem-phone line assembly from a known, verified working port with the serial cable-modem-phone line assembly of the suspected bad port.
    1. Make sure the working port and the suspected bad port are configured Identically.
    2. Swap the entire serial cable-modem-phone line assembly from the working port to the suspected bad port.
    3. If the problem follows the serial cable-modem-phone line assembly from the suspected bad port to the working port then there is a problem in the serial cable, the modem or the phone line. Swap these elements out one by one with known working elements until you have narrowed down the culprit hardware.
    4. If the problem stays with the suspected bad port after swapping the serial cable-modem-phone line assembly then you may have a bad port. Call Lucent Technical Support to confirm.