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CHAPTER 6: Troubleshooting
SYMPTOM: TD and RD LEDs indicate data activity, but data
communication doesn’t exist.
1. Check the wiring of the EIA-232 port (see
Section 3.2
).
2. Check the setting of the DTE/DCE jumper
(see
Section 3.3
).
SYMPTOM: Transmitted and/or received data is full of errors
(garbled data).
1. Check for reversal of polarity on the four-wire
connection. Refer to
Section 3.1
and Figure 2.
2. Check word structure and speed settings on
your computing equipment for consistency.
3. Wire the High Speed SHM-B Async units back-
to-back, eliminating the twisted pair; see if you
still have errors.
• If you do have errors, then test each High
Speed SHM-B Async individually in the
following way. Loopback one High Speed SHM-
B Async’s Transmit-to-Receive by using two
short pieces of wire. Connect that High Speed
SHM-B Async to a dumb terminal and key-in
characters; look for a good loopback. A good
loopback verifies a High Speed SHM-B Async
in proper working condition.