Mitsubishi Electric MELSEC iQ-R Series User Manual page 249

■When C24 is designated to "Non-priority"
Target device
CPU module
SD(TXD) (Send Data)
RS(RTS) (Send Request)
CS(CTS) (Send Possible)
CD(DCD)
(Data Carrier Detect)
RX(RXD) (Receive Data)
The contents of steps  and  below are different from those of the case "Priority" is designated.
 When transmitting data, check the C24 CD (DCD) signal. If the CD (DCD) signal is OFF, turn ON the C24 RS (RTS) signal.
If the CD (DCD) signal is ON, wait until it is turned OFF, then turn ON the RS (RTS) signal.
 Transmit the data after turning ON the RS (RTS) signal.
 After data transmission is completed turn OFF the RS (RTS) signal.
 If the CD (DCD) signal is turned ON during data transmission, terminate data transmission and turn OFF the RS (RTS)
signal, and perform the data receive processing. (Simultaneous transmission occurred.)
 After transmission from the target device is completed, transmit the data terminated at step  from the beginning or
*2
terminated part of the data.
*1 The data equivalent to the setting value of "simultaneous transmission priority/non-priority" is not transmitted.
*2 The data is transmitted from the beginning or from the part where the last transmission has been terminated according to the settings of
"Retransmission time transmission method".
■Remarks
When using the DTR/DSR transmission control function, transmit data from the target device to C24 as shown below in both
cases above. (Page 236 DATA COMMUNICATIONS USING DC CODE TRANSMISSION CONTROL)
• When the C24 DR (DSR) signal is turned OFF, terminate data transmission.
• When the C24 DR (DSR) signal is turned ON after data transmission is terminated, restart data transmission (transmit from
the terminated part of the data).
Data A
Send
request Time for
transmitting
2 characters
Data A
Ò
Ó
CD check CD check
12 DATA COMMUNICATIONS USING HALF-DUPLEX COMMUNICATIONS
Data C
Data B
Since the C24 does not have priority,
Send
request when the CD(DCD) signal is turned
ON, it terminated transmission.
Ô
Data B
Õ
CD check
Data C
The C24 stores the received data.
12.2 Data Transmission and Reception Timing
Continue data
transmission.
Data B
(*2)
Data B
Ö
CD check
Transmission wait time (*1)
12
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