Mitsubishi Electric Melsec Q Series User Manual page 199

6 DEDICATED INSTRUCTIONS
[Operation of the local station when the REQ instruction is being executed]
Sequence program
REQ instruction
Send/receive
instruction flag
Completion device
Status display device at
completion
6 - 32
(3) The data link instruction and instructions for the Ethernet network system cannot
be executed at two or more locations for the same channel.
If the execution conditions are met at two or more locations at the same time,
instructions to be executed later have to wait until the channel becomes available
because handshaking is automatically performed at the execution of the first
instruction.
(4) Whether the REQ instruction is being executed or has been completed normally
or abnormally can be checked with the complete device (D2) or completion status
display flag ((D2) + 1) designated in the set data.
(a) Completion device (D2)
Turns on at the END processing of the scan where the REQ instruction is
completed, and turns off at the next END processing.
(b) Status display device at completion ((D2) + 1)
Turns on and off depending on the completion status of the REQ instruction.
Normal completion: Stays off and does not change.
Abnormal completion: Turns on at the END processing of the scan where
END END
processing processing
ON
OFF
ON
OFF
OFF
OFF
(5) When the instruction is executed using J.REQ/G.REQ, the next write processing
is executed in succession after one processing is completed while the
send/receive instruction flag is on.
When the instruction is executed using JP.REQ/GP.REQ, the processing is
executed only once when the send/receive instruction flag switches from off to on
(at rise).
the REQ instruction is completed, and turns off at
the next END processing.
REQ instruction
execution is completed
MELSEC-Q/L
END END
processing processing
ON
Abnormal
ON
completion
Normal
completion
One scan
6 - 32