Mitsubishi Electric FX5 User Manual page 150

The time-out flag does not automatically turn OFF. Reset using program. While it remains ON, the PLC cannot receive the
next set of data. When the receiving completed flag is set to OFF, the time-out flag is also set to OFF.
Using this function, the PLC can receive data from equipment where the amount of send data varies without the terminators.
■When the control line is set to interlink mode
When the interlink mode is set in the communication parameters, the following sequence is adopted from the start of receiving
to completion:
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.
■Precautions for receiving
When receiving data, please take care about the following.
• While the receiving completed flag is ON, the PLC cannot receive the next set of receive data. When the receiving
completed flag is set to OFF, the PLC waits to receive.
• If the RS2 instruction is driven while the amount of received data "n2" is "0", the receiving completed flag turns ON. To
make the PLC wait to receive, set the amount of received data (n2) to 1 or more, and set the receiving completed flag from
ON to OFF.
• Set the amount of received data to a value including "terminators", "sum check" and "CR+LF". If the specified amount of
received data is less, the serial communication error flag turns ON. When the terminator is set to [Do Not Add] in the
communication settings, an error does not occur.
Full-duplex, bi-directional communication operation
■Send completed  start send operation
When sending of the data is completed, the sending request flag is automatically set to OFF.
When RS2 instruction is executed again after the sending request flag is set to ON, the PLC starts to send.
■Send completed  start receive operation
For full-duplex, bi-directional communication, send and receive can operate simultaneously.
For the operation timing of send completed and start receive, refer to the following.
• Operation during data send (Page 146)
• Operation during data receive (Page 147)
■Receive completed  start send operation
For full-duplex, bi-directional communication, send and receive can operate simultaneously.
For the operation timing of send completed and start receive, refer to the following.
• Operation during data send (Page 146)
• Operation during data receive (Page 147)
■Receive completed  start receive operation
Receiving completed flag turns ON when receiving is completed.
While the receiving completed flag is ON, the PLC cannot receive new data.
When the receiving completed flag is reset, the PLC waits to receive (the state where it can receive data).
5 NON-PROTOCOL COMMUNICATION
148
5.7 Programming