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MELSEC-Q
4 THE EXCHANGE BETWEEN THE PLC AND BUFFER MEMORY
(c) When the CPU (self station) with the communication module attached is a
MELSEC three-tier master station, data from the self station and master
station of the two-tier loop and all local stations and remote I/O stations
within the three-tier loop can be accessed.
Only the buffer memory of the special function module can be accessed for
remote I/O stations.
(Local Station #1)
self
station
(Master
Station)
Communication Module
(Local Station #1)
(Local Station #2)
Remote Station #2
Local Station #3
Master Station
The names in
parentheses are
station names
under a three-tier
system.
The setting to determine to which PLC communication is to be made is
performed by specifying the station number within the same loop of self
station. However, when performing access to the self station, the station
number is specified as 255.
Local Station #64 (Station Number 64)
Always specify
255 when
becoming
a self station
…
Master Station (Station Number 0)
Local Station #1 (Station Number 1)
Local Station #2 (Station Number 2)
Specified to 0
Specified to 1
Specified to 2
Specified to 64
…
Location Station #1
Remote Station #2
Local Station #3
Master Station
Local Station #1
Remote Station #2
Master Station
Self station
Communication Module
255
1
0
0
255
255
1
3
2
Example 1
Example 3
Communication Module
The numbers within
the is the specified
station number.
Example 2
2
(Local Station #1)
Self
station
(Master
Station)
Communication Module
(Local Station #1)
(Local Station #2)
Remote Station #2
Local Station #3
Master Station