Mitsubishi Electric MELSEC Q Series Reference Manual page 340

(c) Checking the execution status of the READ instruction
The execution status of the READ instruction (Normal completion, Error completion) can be checked with the
following devices specified in the setting data.
• Completion device (D2)
Turns ON in the END processing for the scan after completion of the READ instruction, and turns OFF in
the next END processing.
• Completion status indication device ((D2)+1)
Turns ON in the END processing for the scan after completion of the READ instruction, and turns OFF in
the next END processing, only when the READ instruction has failed.
(d) Operation in READ instruction execution
• Operation of the own station
Program of own station
READ instruction
Start contact
Completion device of
own station (D2)
Completion status indication
device ((D2)+1)
338
END processing END processing
READ instruction execution
ON
OFF
OFF
OFF
END processing END processing
Reading from the device specified
by READ completed
ON
ON When failed
Normal completion
1 scan