Omron CJ1W-SCU32 Operation Manual page 148

4 Using Protocol Macros
Additional Information
If continuous I/O refreshing is specified for the data exchange method for link words, I/O refresh-
ing is executed during the execution of protocol macros between the CPU Unit and the Unit with-
out synchronizing with the execution of Send/Receive commands. Therefore it is necessary to
pay attention to the data exchange method at the start and end of the protocol macros.
(1) The new data may not be sent by the Send command in a protocol macro that is executed
immediately after the send data in memory in the CPU Unit is updated.
The send data is transferred to the Unit in the I/O refresh period before it will be sent by the
Send command.
(2) Data received by a Receive command in a protocol macro may not be reflected in the receive
data area of the CPU Unit if execution of the protocol macro is terminated immediately after
the Receive command.
If the protocol macro is still executed during the I/O refresh period after the data is received
by the Receive command, the receive data will be refreshed in the memory of the CPU Unit.
"Continuous I/O refreshing" in the Data exchange method for link words is suitable for applica-
tions in which Send/Receive commands are executed repeatedly in the one protocol macro
(ExecPMCR instruction).
If data in the CPU Unit is to be sent with a Send command in the next ExecPMCR instruction or
receive data for a Receive command is to be reflected in the CPU Unit and then the protocol
macro ended, use the "on-request I/O refreshing" setting.
4-12 CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)