Omron CJ Series Connection Manual page 56

No. Outline
2.3. Normal/error
detection processing
Detects a normal end or an error end of the result of
send/receive processing.
It is considered as a normal end when all the following
conditions are satisfied.
・Normal end of CMND instruction (No CMND instruction
error)
(Condition of ''No communication error'' is included in (1).)
・Normal messages received from Destination Device
(No Destination Device error)
If any of the errors are detected under the conditions above,
a corresponding error flag turns ON.
Description
9．Program
53