Mitsubishi MELSEC-A series, Programming Manual

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6. BASIC INSTRUCTIONS
6
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84
MELSEC-A
Execution (1) Data communication using the COM instruction
Conditions
1) Example without using the COM instruction
2) Example using the COM instruction
3) By using the COM instruction in the master station, data communication can
be made faster as the number of data communication times with the remote
I/O station can be increased unconditionally as shown in Example 2).
4) Data may not be received as shown in Example 1) when the scan time of the
local station sequence program is longer than that of the master station
sequence program. By using the COM instruction in the local station, data
can be received securely.
5) By using the COM instruction the local station, a link refresh is made every
time the local station receives the master station command between:
(a) Step 0 and COM instruction
(b) COM instruction and COM instruction
(c) COM instruction and END instruction
(2) Even if the COM instruction is used in the master station, data communication
cannot be made faster when the link scan time is longer than the master station
sequence program scan time.
Master station program
Data communication
Local station program
Remote I/O station
I/O refresh
Master station program
Data communication
Local station program
Remote I/O station
I/O refresh
Sequence program
link scan