F-56
FX Series PLC User's Manual - Data Communication Edition
Non-Protocol Communication (RS/RS2 Instruction)
8 Creating Programs (RS2 Instruction)
8.2 How to Use RS2 Instruction
3. Operation of time-out check flag
When data receiving is suspended, if the PLC does not receive the next set of data within the preset time-out
time setting, the time-out check flag is set to ON.
At this time, the receiving complete flag is also set to ON.
The time-out time setting can be set to a value from 1 to 255 (10 ms to 2550 ms).
The time-out check flag does not turn OFF automatically. Set it to OFF in the sequence program. (When the
receiving complete flag is set to OFF, the time-out check flag is also set to OFF.)
By using this function, the PLC can receive data from equipment where the amount of send data varies
without the terminator.
4. When the control line is set to the interlink mode
When the interlink mode is selected in the communication format, the following sequence is adopted from
start of receiving to completion of receiving:
1) When the amount of data already received becomes "preset amount of received data -30", the control line
ER (DTR) turns OFF.
When the control line ER (DTR) turns OFF, the external equipment should suspend data sending.
After the control line ER (DTR) turns OFF, the PLC can receive up to 30 characters (bytes).
2) When the external equipment suspends data sending, the PLC sets the time-out check flag and receiving
complete flag to ON after the preset time-out time setting.
Move the received data in a sequence program, and then set the receiving complete flag and time-out
check flag to OFF.
3) When the receiving complete flag is set to OFF, the control line ER (DTR) turns ON.
When the control line ER (DTR) turns ON, restart data sending from the external equipment.
4) Repeat steps 1) to 3) until data receiving is completed.
5. Cautions on receiving
When receiving data, observe the following cautions
1) While the receiving complete flag is ON, the PLC cannot receive the next set of receive data.
When the receiving complete flag is set to OFF, the PLC waits to receive.
2) Set the amount of received data to a value including "terminators", "sum check" and "CR+LF".
If the specified amount of received data is small, the serial communication error flag (M8063 or M8438)
turns ON.
Name ch1 ch2
Time-out check flag M8409 M8429
Time-out time setting D8409 D8429
Receive data is suspended.
Set to OFF in sequence program.
Receiving
D8409
×
10 ms
Data
ON
Time-out check flag
M8409
ON
Receiving complete
M8403
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