Operation Of Control Line - Mitsubishi Electric FX3U-232-BD User Manual

FX Series PLC User's Manual - Data Communication Edition
Non-Protocol Communication (RS/RS2 Instruction)
8.3

Operation of Control Line

FX , FX , FX
3S 3G
executing half-duplex, bidirectional communication, pay attention not to set the sending request to ON while
receiving. If the sending request is set to ON, the PLC starts to send. As a result, the external equipment may
not be able to receive data, and the sent and received data may be destroyed.
In full-duplex, bidirectional communication, the sending wait flag M8371, M8401, and M8421 does not turn
ON.
However, the sending wait flag M8371, M8401, and M8421 remains ON while the DR (DSR) is OFF, the PLC
waits to send, and the control line is in the standard mode or interlink mode.
1. When the control line is not provided
RS2
instruction
OFF ON
driving
SD (TXD)
Send data
Sending
OFF
request
M8402
RD (RXD)
Receive data
Receiving
complete
M8403
F-72
, FX and FX
3GC 3U 3UC
Message
1
ON
Message
2
OFF
Receiving wait status
is started.
PLCs execute full-duplex, bidirectional communication. When
Message Message
3
Message 4
ON
Reset it in a sequence program.
While it remains ON, the PLC cannot receive the next
set of data.
8 Creating Programs (RS2 Instruction)
8.3 Operation of Control Line
5
ON