Mitsubishi FX2N RS485 communication

[Jirrr]

Hello,
I would like to use RS function for communication with another PLC....
I have FX2N-485BD modul....connected two wires
Sending from PLC works but receiving no,it always received data I sent and wait to reset flag M8123 is there any way to get rid of this echo???
/M8120 = H6F,receive buffers set 4 bytes/

Thanks a lot....

 

[gclshortt]

http://dl.mitsubishielectric.com/dl/fa/document/manual/plc_fx/jy992d69901/jy992d69901e.pdf

This appears in the manual in the following section:
3.3 Using RS-485 Interface
You could change your wiring to 2 pairs instead of the 1 pair.

Regards,

 

[lfe]

If the other PLC is a FX2N or FX1N you can interchange data using Parallel Link and then you don't need to use RS instruction.

Anyway D8120 has 16 bits and with H6F you only specify 8 bits and if I remember well you need to put to one some of the high bits to specify RS485, look at the manual.

 

[Jirrr]

Thanks a lot....

I woud like to use 2-wires because there is 2-wires network and 2-wires hardware....(there are some some termocouplers transmitters and siemens S7-1200s)

with D8120 You are right there is different meaning for computer link and non-protocol....I set it to H0C6F (modem mode rs485)...now I can receive but only 1 byte a time(after 4 bytes received bit M8123 goes up)..I need 4....so now I must send each byte separately,if I try send 4 bytes in one message I got error 6301 /Parity, overrun or framing error/...
RS have send and receive buffers both set to 4....Is it possible that I overlooked something??

Thanks....J

 

[Jirrr]

to be more precise...I need to send from FX2N 485BD this "#01A" and receive from transmitter 8 numbers(separated by comma) from 8 thermocoupler channels....all this using RS function...sending is OK but still I have no way to receive answer...(this is no problem with simatic or any PC terminal program but my hardware is FX2N mitsubishi)....

Thanks for any suggestion....

 

[lfe]

- Are you trying to communicate with an Advantech 4000 series module or similar?

- if that protocol uses characters such as # then it surely transmits and receives ASCII characters, so if you need to transmit 0 then the ASCII representation of zero must be sent and not a byte equal to zero.

- if a protocol sends and receives ASCII characters it will probably use data length 7bit and not 8bit, it is also rare that you choose 2bit stop, I have never seen it before.

- Data length, stop bits, parity and baud rate must be exactly the same on both sides of the communication.

- Note that the 485BD module is not isolated, that can cause problems if the module and the PLC do not share exactly the same common power. Use of an insulator module between both would be highly recommended. I installed in the past hundreds of FXnN PLC connected to Advantech modules but I always use an RS232 BD FX module port connected to an RS232 to RS485 isolation converter.

- if you have to receive 8 numbers separated by commas you are using a reception buffer too small

 

[Peter Nachtwey]

I have done this. I wrote a program to communicate with one of our motion controllers. The effort it took far outweighed the cost of the PLC. The code took up a lot of the FX2N's resources. Unless there are going to be many of these, I would not waste the time.
https://deltamotion.com/files/rmcfx.zip
Yuk. It has been about 20 years since I wrote this.

 

[Jirrr]

Thanks a lot...

Yes...it is some Chinese version of IPCCON i-7018.....as for comm parameters,I tested it with PC terminal it worked (send ##05$0D from PC...received >+25.111+25.123...etc./no comma separator/]

Not working this way with FX2N....so I tested it with PC terminal...
FX2N works like this for me:
1.from PLC sent "TEST",on PC I received "TEST"
2.as echo(TEST) is immediately in PLC buffer I reset bit M8123
3.sent "1234"from PC..on PLC I got error 6301 /Parity, overrun or framing error/
4.reset error..then sent "1" from PC and received "1" in PLC D8123 counts 1
repeated sent 3 more times D8123 counts 4(RS send and receive buffer set to 4) and M8123 went 1...

So my problem is why PLC can receive only 1 byte a time without error a no more??

PS:thanks Peter..I will look at it later....