Rockwell Automation 1791-XXXX ANALOG BLOCK I/O - Manual (Page 69)

Troubleshooting
Chapter 8
8-2
Table 8.A
Troubleshooting Chart
Indication Description
Power OFF
ON
No power
Power okay
COMM OFF
ON
Flashing
Communications not established
Communication established
Reset commands being received in Program mode
FAULT OFF
ON
Flashing
Normal
Error (hardware or software), block power low
COMM FAIL - communication cable disconnected, 100ms between valid
frames, no more than 255 valid frames between valid frames addressed to
block, 20ms idle time exceeded.
COMM and FAULT will alternately flash when processor restart lockout is selected, a fault has occurred and the processor is
communicating with the block.