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Using the Message Service Section 6-3
6-3 Using the Message Service
With SEND, RECV, and CMND, the Network Instruction Enabled Flag and
Network Instruction Error Flag are generally written into the program as input
conditions, as shown below. Only one instruction can be executed at a time for
any given communications port. Exclusive control thus must be incorporated
to execute two or more instructions per operating level with C200HX/HG/HE
PLCs, nine or more instructions with CS/CJ-series, CVM1, and CV-series
PLCs (because CVM1 and CV-series PLCs have eight ports), or two or more
instructions with CQM1H-series PLCs.
SEND/RECV Flags
CS/CJ-series PLCs
Note With CS/CJ-series PLCs, ports 0 to 7 are also used for executing the PMCR
(Protocol Macro) instruction, therefore these flags are used for the 4 instruc-
tions, SEND/RECV/CMND/PMCR. When the PMCR command is being exe-
cuted, the same port cannot be used for SEND/RECV/CMND instructions.
KEEP A
Keep instruction
Turns A ON from beginning to completion of
communications instruction.
Reset B
A
Operand and
control data cre-
ation by @MOV
and @XFER
Communications
instruction
@SEND
@RECV
@CMND
Creates operand and control data in a given area.
Executes communications instruction.
Network Instruction
Enabled Flag
A
Startup differ-
ential
DIFU B
Creates reset input. (Turns reset B ON after execution of
communications instruction.)
Network Instruction Error Flag
Network Instruction
Enabled Flag
A
Reset D
In case of Send Error Flag, re-send processing
can be executed.
Establishes exclusive control so that no communications
instruction is started before the previous one has been
completed.
Exclusive control to prevent simultaneous execution:
(Continues in the same way.)
Active Node Flag for
source node
Active Node Flag for
destination node
A
Execution
condition
KEEP C
Keep instruc-
tion
C
Execution
condition
Network Instruction
Enabled Flag
Name Address Contents
Word Bit
Network Instruc-
tion Enabled Flag
A202 Port number corresponds
to bit number, i.e., port 0:
bit 00, port 1: bit 01, etc.
0: Execution not enabled (executing)
1: Execution enabled (not executing)
Network Instruc-
tion Error Flag
A219 Port number corresponds
to bit number plus 8, i.e.,
port 0: bit 08, port 1: bit 09,
etc.
0: Normal end
1: Abnormal end