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Enhanced Protocol Macro Functions Section 5-6
Therefore, when a send command is executed in a step, the send message is
compiled immediately based on data read from the Board/Unit, and the actual
message is sent. Therefore, the actual message transmission is performed
immediately when the send command is executed (there is no need to wait
until the next I/O refresh with the CPU Unit). The receive command operation
is similar. When the receive data is stored in the Board/Unit, receive com-
mand execution is completed. The actual received data is stored in I/O mem-
ory at the next I/O refresh with the CPU Unit.
• Setup Area Allocated in the DM Area
m = D30000 + 100
× unit number
Note When “continuous I/O refreshing” is specified for the link word specification
data exchange timing, the normal I/O refresh will be executed with the CPU
Unit while protocol macros are being executed without syncing with execution
of the send and receive commands. You must therefore be careful of the data
exchange timing at the start and end of 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 must be read to the SCU/SCB 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 re-
freshed in the CPU Unit if execution of the protocol macro is completed im-
mediately after the receive command. If the protocol macro is still being
executed during the I/O refresh period after the data is received by the re-
ceive command, the receive data will be refreshed in memory in the CPU
Unit.
The “continuous I/O refreshing” setting is suitable for applications in which
send/receive commands are executed repeatedly in the same protocol macro
(i.e., the same PMCR). If data in the CPU Unit is to be sent with a send com-
mand in the next protocol macro or receive data for a receive command is to
be refreshed in the CPU Unit and then the protocol macro ended, use the “on-
request I/O refreshing” setting.
Words Bit Setting
Board Unit
Port 1 Port 2 Port 1 Port 2
D32008 D32018 m+8 m+18 02 Link word specification data
exchange timing
0: On-request I/O refreshing
1: Continuous I/O refreshing
PMCR
CPU Unit
Ladder program
I/O memory
Receive data
Send data
Board/Unit
Step 0
Step 1 (send)
(2)
(1)
Execution
instruction
IN
OUT
Receive data
Send data
I1
O1
Read, compile message
(3) Send
R (O1, 2)
Link word 1
Communications
sequence
(1) to (4) are performed in
order for the processing
within this dotted line.
Send message according
to send command
The refresh timing continuously refreshes I/O regardless of
the any request from the Board/Unit (using send/receive
commands in the communications sequence).
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