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4 Using Protocol Macros
4-20
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
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Full-duplex Mode
There is a 2.5 KB reception buffer for each serial port in full-duplex mode of NJ-series Protocol
Macro Mode. When flow control is used, initiate flow control after receiving about 2 KB, and then
release control after processing all but 0.5 KB of receive data. The Unit can store up to 1,000 bytes
(500 words) of data for each Receive command if 2 KB of receive data is first stored in the buffer and
1,000 bytes (03E8 hex) is set as the maximum number of send/receive data bytes.
Note Signal names used are those at the Serial Communications Unit.
1
With full-duplex protocol macro communications, the RTS (RS) signal is turned OFF when 2 KB
of data is in the reception buffer (i.e., with 0.5 KB remaining).
2
The receive data (RD signal) from the remote device is 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 Recv command.
4
When matching data is found, all the previous data is deleted from the reception buffer.
5
When the amount of data stored in the reception buffer decreases to less than 0.5 KB (i.e., more
than 2 KB remaining), the RTS (RS) signal will turn ON.
6
Data that is received while the ExecPMCR instruction is not being executed is discarded.
7
In full-duplex mode, the data left over after the analysis performed with the last Recv command
and any subsequent data received while the ExecPMCR instruction is stopped is discarded.
During this interval, you cannot use RS flow control.
Receive Receive Receive Send Send
ExecPMCR instruction ExecPMCR instruction
SD signal
RD signal
RTS (RS)
signal
RS turned ON when only
0.5 KB in buffer.
RTS (RS) signal turned
OFF when 2 KB of
data accumulates in
reception buffer. Data received from the end of the
last Recv command until the next
ExecPMCR execution is discarded.
The RTS (RS) signal does not operate.
Command