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MELSEC-Q
4 THE EXCHANGE BETWEEN THE PLC AND BUFFER MEMORY
4.2.3 Choosing a process
Process requests of PCRD and PCWT instructions are specified using values referred
to as process codes. For details, see the descriptions of the PCRD and PCWT
instructions.
4.2.4 Bit/Word designation
Bit/Word designation refers to the designation of processing in 1-bit units or 1-word
(16-bit) units when the PLC accesses the bit device.
Only one point
is accessed
Bit
designation
16 points are
accessed
as a group
Word
designation
M0
to
M0
to
M15
M8 M7
When word-unit process is specified, 16 bits of process points will be specified. Also,
when word-unit is specified, the starting number of the respective device must be
specified as 0 or a multiple of 16.
Example
For M,
M0, M16, M32,
• • • •
are used as starting numbers.
For B,
B0, B10, B20,
• • • •
are used as starting numbers.
When processing special relay M in word units, the starting number may be 9000
or a multiple of 16 added to 9000.
(M9000,
M9016,
M9032,
can be used as starting numbers.)
…………
When accessing word devices, use word unit processing.
REMARK
Access • • • I/O processing such as data read and write.
