User manual

Troubleshooting
Remote I/O 5-20
Classic PLC-5
processors only
troubleshooting – remote I/O system, 1771-ASB series C and series D continued...
1
You must select the operating mode of the remote I/O adapter module as outlined in the publication furnished with the remote I/O
scanner/distribution panel, remote I/O scanner-program interface module, or I/O scanner-message handling module. Pay close attention to the
disable search mode in the 1772-SD, -SD2.
2
The I/O chassis is in faulted mode as selected by the last state switch on the chassis backplane.
3
Cycling power clears the block-transfer request queue. All pending block transfers are lost. Your program must repeat the request for block
transfers from the chassis.
4
If a fault occurs and the processor is in the run mode but is actually operating in the dependent mode, the chassis fault response mode is
selected by the last state switch on the chassis backplane.
☞
Indicators
Active Adapter
Fault
I/O
Rack
Description Probable Cause Recommended Action
Off Off Off module not
communicating
• power supply fault
• wiring from scanner to adapter module
disrupted
• scanner not configured properly
• one faulted chassis within a rack group
address causing scanner/distribution
panel to fault all chassis in rack group
address (when in disable search mode)
• Check power supply, cable connections,
and make sure adapter module is fully
seated in chassis
• Correct cable and wiring defects
• Refer to publication 1772-2.18 for
scanner configuration
• Check sequentially from the first module
to the last module to pinpoint fault; correct
any faults and proceed to the next chassis
ACTIVE
ADAPTER
FAULT
I/O RACK
FAULT