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4 Using Protocol Macros
4-10
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
Link word specification is a method that specifies the storage location of send/receive data when you
execute communications sequence by using the protocol macros (method that specifies area to share
data between the CPU Unit and Unit).
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On-request I/O Refreshing
Link words are refreshed between the CPU Unit and Unit at every CPU Unit cycle.
The actual refresh timing with the CPU Unit, however, does not correspond to whenever the I/O is
refreshed. I/O refresh is performed at the next I/O refreshing after the CPU Unit receives a request
from the Unit (according to the Send/Receive command executed in the communications sequence,
and it does not synchronized with the CPU Unit cycle). This is called on-request I/O refreshing.
Level Item Possible changes in settings
Sequence
parameters Transmission control
parameters Setting change unnecessary.
Link words
Response notifica-
tion method
Receive Wait Moni-
toring Time Tr The monitoring times are set to 3 seconds for most sequences. The set-
tings are different for send-only and receive-only sequences, as well as
for sequences that require time for responses.
Receive Finished
Monitoring Time Tfr
Send Finished Moni-
toring Time Tfs
Step parame-
ters Repeat counter Setting change unnecessary.
Command
Retry count The retry count is generally set to 3 retries (4 tries total) for sequences
that use the Send&Recv command. Different settings are used for
sequences that have other commands.
Send wait time Setting change unnecessary.
Send message
Receive message
Response write
enable
Next process
Error process
4-1-4 Data Exchange Method for Link Words