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(4) MELSECNET/H (remote I/O network)
The link refresh of the remote master station is performed by the "END processing" of the CPU module.
Since link scan is performed at completion of link refresh, link scan 'synchronizes' with the program of the CPU module.
When the ZCOM instruction is used at the remote master station, link refresh is performed at the point of ZCOM
instruction execution, and link scan is performed at completion of link refresh.
Hence, use of the ZCOM instruction at the remote master station speeds up send/receive processing to/from the remote
I/O station.
(1) When the ZCOM instruction is not used
Remote master
0
station program
Link scan
Remote I/O station
network refresh
I/O module
Intelligent
function module
(2) When the ZCOM instruction is used
Remote master
0
station program
Link refresh
Link scan
Link refresh
Remote I/O station
network refresh
I/O refresh
I/O module
Auto refresh
Intelligent
function module
For details on the transmission delay time on MELSECNET/H (remote I/O network), refer to the manual below:
• Q Corresponding MELSECNET/H Network System Reference Manual (Remote I/O network)
(5) The ZCOM instruction can be used as many times as desired in sequence programs.
However, note that each execution of a refresh operation will lengthen the sequence program scan time by the amount of
time required for the refresh operation.
(6) Designating "Un" in the argument enables the target designation of the intelligent function as well as the network
modules.
In this case, the auto refresh is performed for the buffer memory of the intelligent function modules. (It replaces the
FROM/TO instructions.)
(7) Only with the Universal model QCPU and LCPU, interruption of processing is enabled during the execution of the ZCOM
instruction. However, when refresh data are used in an interrupted program, the data can split.
1. The ZCOM instruction cannot be used in a fixed cycle execution type program or interrupt program.
2. The Redundant CPU has restrictions on use of the ZCOM instruction.
Refer to the manual below for details.
• QnPRHCPU User's Manual (Redundant System)
END
0
Link refresh
Link refresh
I/O refresh
Auto refresh
ZCOM
ZCOM
END
0
0
END
END
ZCOM
END
0
END
S.ZCOM, SP.ZCOM
0
0
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