Mitsubishi MELSEC Q Series Programming Manual page 872

ZCOM
(4) Remote I/O network (QCPU only)
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.
Remote master
station program
Link scan
Remote I/O station
network refresh
I/O module
Intelligent
function module
Remote master
station program
Link scan
Remote I/O station
network refresh
I/O module
Intelligent
function module
For details of the transmission delay time on the 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.
8-4
(1) When the ZCOM instruction is not used
0
END 0
Link refresh
Link refresh
I/O refresh
Auto refresh
(2) When the ZCOM instruction is used
ZCOM
0 END 0
Link refresh
Link refresh
I/O refresh
Auto refresh
0
END
ZCOM ZCOM
END
0
0
END
END 0