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4-19
4 Using Protocol Macros
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
4-2 De
vic
e
V
ariab
les
fo
r CJ
-series Un
it and
Sys
tem-defined
V
ariables
(Pr
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toco
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4
4-2-2 Area Descr
ipt
ions
z
Half-duplex Communications
With NJ-series half-duplex protocol macro communications, flow control can be released by turning
ON the RTS (RS) signal (CTS (CS) signal at the Remote Unit) while the Recv command is executed.
Note Signal names used are those at the Serial Communications Unit.
1
With protocol macro communications in half-duplex mode, the RTS (RS) signal is ON only while
the Receive command is being executed.
2
The receive data (RD signal) from the remote device is initially stored in the reception buffer.
3
The data in the reception buffer is analyzed, and a search is performed for data matching an
expected message registered with the Receive command.
4
When matching data is found, the RTS (RS) signal is turned OFF. The search starts after the
final data is received. It takes between 100
µ
s and 4 ms from the start of the search until the
RTS (RS) signal turns OFF.
5
While the Send command is being executed, and while the ExecPMCR instruction is not being
executed, the RTS (RS) signal stays OFF and receive data is discarded.
RS/CS Flow Control
ExecPMCR instruction
ExecPMCR
instruction
Command
SD signal
RD signal
RTS (RS)
signal
RTS (RS) turned OFF
after 0.1 to 4 ms
RTS (RS) signal ON
while Receive
command is
executed. Data received before
Send is completed is
discarded. Data received while the ExecPMCR
instruction is not being executed is
discarded (controlled by turning
OFF the RTS (RS) signal).
The OFF status of the RTS (RS)
signal is maintained after execution
of the ExecPMCR instruction.