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■CC-Link IE Controller Network and MELSECNET/H (PLC to PLC network)
When the scan time for the sequence program of host station is longer than the scan time for the other station, the ZCOM
instruction is used to ensure the data reception from the other station.
• Example of data communications when the ZCOM instruction is not used
Control station
program
Link scan
Normal station
program
• Example of data communications when the ZCOM instruction is used
Control station
program
Link scan
Normal station
program
For details on the transmission delay time on CC-Link IE Controller Network and MELSECNET/H (PLC to PLC network), refer
to the manuals below:
MELSEC-Q CC-Link IE Controller Network Reference Manual
Q Corresponding MELSECNET/H Network System Reference Manual (PLC to PLC network)
When the link scan time is longer than the sequence program scan time, data communications will not be faster even if the
ZCOM instruction is used.
Sequence program 0
Link scan
8 INSTRUCTIONS FOR DATA LINK
822
8.1 Network Refresh Instructions
0
END
0
END
0
0
END
0
END
0
END
0
END
0
0
END
0
END
ZCOM
ZCOM
ZCOM
END
0 ZCOM
END
0
END
0
ZCOM
END
END 0 ZCOM
0
ZCOM
END
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