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3 COMMUNICATION BETWEEN THE PLC CPU AND THE MOTION CPU IN
THE MULTIPLE CPU SYSTEM
3.3 Reading/Writing Device Data
Device data can be written or read to/from the Motion CPU by the PLC CPU using the
dedicated instructions listed in the table below.
Refer to Chapter 5 "MOTION DEDICATED PLC INSTRUCTIONS" for the details of
each instruction.
(Data cannot be written or read to/from the PLC CPU by another PLC CPU, to/from the
PLC CPU by the Motion CPU, or to/from a Motion CPU by another Motion CPU.)
Instruction name Description
S(P).DDWR
Write a device data of the self CPU (PLC CPU) to a device of the other
CPU (Motion CPU).
S(P).DDRD
Read a device data of other CPU (Motion CPU) to a device of the self
CPU (PLC CPU).
For example, by using the S(P). DDWR dedicated instruction, the device data of the
PLC CPU can be written to the device data of the Motion CPU.
<Example>
PLC CPU Motion CPU
S(P). DDWR instruction
Write device
memory.
Read device memory
Device memoryDevice memory
POINT
(1) One PLC CPU can execute a total of up to 32 "Motion dedicated instructions"
and "dedicated instructions excluding the S(P). GINT" simultaneously.
When Motion dedicated instructions and dedicated instructions excluding the
S(P). GINT are executed simultaneously, the instructions will be processed in
the order received.
If the command which has not completed processing becomes 33 or more, an
OPERATION ERROR (error code: 4107) will be occurred.
(2) Data refresh via the S(P). DDRD/S(P). DDWR is not synchronized with data
refresh via the automatic refresh function of shared CPU memory.
Do not issue S(P). DDRD/S(P). DDWR instructions to the devices whose data
in shared CPU memory is being refreshed.