1.6.2 I/O No. of PLC CPU and Q173CPU(N)/Q172CPU(N)
In the Multiple CPU system, I/O No. is assigned to the PLC CPU/Motion CPU to
enable communication between the PLC CPU and Motion CPU using the following
• The Multiple CPU dedicated instructions
• The Motion CPU dedicated instructions
• The Multiple CPU communication dedicated instructions
The I/O No. of the PLC CPU/Motion CPU are fixed based on the installed slots and
cannot be changed.
The table below lists the I/O No. of the PLC CPU/Motion CPU installed in the CPU
base unit of the Multiple CPU system.
CPU installation position
Head I/O number
The I/O No. of the PLC CPU/Motion CPU are used in the following cases:
• When writing data to the shared CPU memory of the self CPU using the S. TO
• When reading data from the shared CPU memory of the other CPU using the FROM
• When reading data from the shared CPU memory of the other CPU using an
intelligent function module device (U \G )
• When reading device data directly from the Motion CPU from the PLC CPU using
the "S(P). DDRD" instruction.
• When writing device data directly to the Motion CPU from the PLC CPU using the
• Refer to Chapter "3. COMMUNICATION BETWEEN THE PLC CPU AND THE
MOTION CPU IN THE MULTIPLE CPU SYSTEM" for communication between
the PLC CPU and the Motion CPU.
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