12 DATA COMMUNICATIONS USING HALF-DUPLEX COMMUNICATIONS
12.5 Considerations for Half-duplex Communications
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12.5 Considerations for Half-duplex Communications
The following describes the considerations for using half-duplex communications.
Half-duplex communications system configuration and functions
Half-duplex communications can be used only in a system configuration where the CPU module and a target device are
connected on a 1:1 basis.
Agreement and confirmation between target device and CPU module
Determine and confirm the following items between the target device and the CPU module.
• Whether or not half-duplex communications can be performed by C24 RS (RTS) signal and CD (DCD) signal.
• C24 RS (RTS) signal and CD (DCD) signal ON/OFF timing
• C24 and target device data transmission timing
• RS-232 cable connection method
Transmission control
When the transmission control function is used, DC1/DC3 transmission control and DC1/DC3 reception control of the DC
code control cannot be used with half-duplex communications. Therefore, do not designate them.(Page 236 DATA
COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL)
CPU CPU CPU
RS-232
RS-232
RS-422/485
CPU
C24
(Half-duplex communications can be designated) (Half-duplex communications cannot be designated)
Target device Target device
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