Problem with receiving data via FX3U-485BD(M8123 not work)

[Mlifman 2]

Hello I have controller FX3U with communication module FX3U-485BD . Communication module FX3U-485BD connected to power supply by one pair wiring. I can send commands and power supply works very good. However I can not receive data from power supply. The open contact M8123 not work. The lamp RD on the communication module FX3U-485BD not light during sending command (command with ? the lamp SD blinking). I am attaching a file with the software. I'd love to help. Power_Supply.pdf PLC_Parameters.pdf

[kaare_t 155]

What kind of power supply are you using, and which protocol?? You have selected "Dedicated Protocol" in the parameters which indicates MC protocol...

[Mlifman 2]

Iam using iDRC Programmable DC power supply(model DSP-100-07.5HD) with RS 485 protocol (one-pair wiring). In setting of power supply I have only RS485 or LAN,and transmission speed(9600) suitable to PLC parameters. Is it necessarry to use M8123 (Receiving complete flag) or M8124(Carrier detection flag)? M8123 has a coil in the programm?

[kaare_t 155]

As a start you should use NoProtocol unless the PS is running MC protocol (which I doubt). When using "Dedicated Protocol" the PLC uses the built-in MC protocol. I must admit I'm not sure why you can actually send correct data to the PS when using Dedicated Protocol. Are you sure that the data are received at the PS correctly??

[Mlifman 2]

I understand your direction about using No Protocol. I will be check it. However in PLC parameters I used Dedicated protocol and PS works very well (Remote control,Reset,OVP,OCP,set voltage,current...) With best regards Michael

[kaare_t 155]

Is it the complete program you've posted in your first post? It is 'impossible' to use RS instruction for send/receive if the BD card is set in "DedicatedProtocol". What DedicatedProtocol does is to automatically configure the card to use MC protocol which is a Mitsubishi generic protocol for communication between Mitsubishi Devices, or your custom MC protocol device. Are you moving data into D8120 somewhere in the program (setting parameters programatically)?? Did you power-cycle the PLC lately (settings may be effective only after a power-cycle of the PLC)? Are you running 2-wire RS485 or 4-wire RS485? If running 4-wire try to interchange the two receive cables on the BD (do not touch the send/SD cables, only the receive/RD cables). Did you use the correct resistors (resistors are most important on short lines)?