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Symptom
Active Indicator light not on.
Active Indicator Flashing
RCV indicator does not flash
when attempting to send data
from an operator interface device.
XMT light does not flash within
two seconds of receiving a signal
on the port (RCV indicator
flashes).
Intermittent Communications
Problem
4-4
Troubleshooting
Table 4-1 Troubleshooting Matrix
Probable Cause
1. No Power to module
2. Defective module
Defective module
Defective module. Most likely a
defective cable. Possibly an
operator interface device failure or
configuration error.
1. Baud rate mismatch
2. Hardware handshaking error.
3. Protocol error.
1. Communications "noise".
2. Ground loop problem
Corrective Action
1. Ensure 5V power is supplied to
the rack
2. Cycle power. If ACTIVE indicator
does not remain on, replace the
module.
Cycle power. If ACTIVE indicator
does not remain on, replace the
module.
Check communications cable
wiring. Replace with a known good
cable and retry. Replace operator
interface device with one known to
be good.
1. Correct baud rate settings.
2. Enable operator interface
hardware handshaking or set
PPX:505-2571 hardware handshake
to DISABLED.
1. Reduce baud rate; replace or
re-route cabling.
2. Ensure proper grounding; install
isolation equipment.
SIMATIC 505-2571 Program Port Expander Manual
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