Omron CQM1 Operation Manual page 28

Bit Allocation
Inputs
Outputs
When a transmission error occurs, the input bits are processed according to
the transmission error processing setting: HOLD or LOAD OFF.
If the input mode is set to 15IN+ERR, the transmission error bit turns ON.
The transmission error bit turns OFF when normal transmission is re-estab-
lished.
The normally received signals are then input to the input bits.
A transmission error with an output B7A Link Terminal can only be detected at
the Link Terminal. Confirm the error with the Link Terminal ERR indicator and
error output.
Section 1-5
9