F-56
FX Series PLC User's Manual - Data Communication Edition
Non-Protocol Communication (RS/RS2 Instruction)
6 Creating Programs (RS Instruction)
6.4 Important Points in Creating Programs
6.4 Important Points in Creating Programs
1) The RS instruction can be used as many times as necessary in a program, but make sure that only one
RS instruction is driven at a time.
For multiple RS instructions to be driven, make sure the OFF time is longer than one scan time.
2) In FX
2(FX), FX2C, FX0N, FX1S, FX1N and FX1NC PLCs, make sure to provide an interval of two scan times
or more between completion of sending and the start of receiving or between completion of receiving and
the start of sending.
In FX
2N PLCs before Ver. 2.00, provide an interval of 100 s or more.
In FX
2N PLCs Ver. 2.00 or later, FX2NC, FX3S, FX3G, FX3GC, FX3U and FX3UC PLCs, this interval is not
necessary.
3) While a RS instruction is being driven, change of D8120 is prohibited.
To change D8120, set the RS instruction to OFF, set D8120 to "0", and then set a new value to D8120.
4) In the interlink mode, set the amount of received data n to "31" or more.
If it is set to "30" or less, the control line ER (DTR) is set to OFF as soon as the PLC receives data. As a
result, the received data may be partially skipped.
5) Do not use another instruction which uses the same communication port. If such an instruction is used,
communication may not function normally.
FX
3S, FX3G, FX3GC, FX3U and FX3UC PLCs: RS2 instruction, IVDR instruction, etc.
FX
2N and FX2NC PLCs: EXTR instruction
6) When RS-485 communication is executed in FX
3U and FX3UC PLCs, it may take 300 s until the PLC
starts receiving after it has completed sending.
Assure 300 s or more in counterpart equipment as the period from completion of receiving to start of
sending.
6.5 Communication Error
When a communication error occurs, the error flag M8063 turns ON and D8063 stores the error code.
Confirm the contents in "Chapter 11. Troubleshooting".
Error code Description
6301 Parity error, overrun error or framing error
6302 Defective communication character
6304 Defective data format
6305 Defective command
6306 Monitoring time out
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