Problem with programming MITSUBISHI FR-A540 via RS-485 cable

[Constantin Climentieff]

Hi everyone! I need some help in programming MITSUBISHI FR-A540 controller. 1. Controller has a RS-485 connector for FR-PU04 board. Can I use this connecror itself, or I must use FR-A5NR only? 2. Controller has pins marked RDA/RDB/SDA/SDB but my computer has RxD+, RxD-, TxD+, TxD-. What is the correct pinout for RS-485 cable? 3. Hardware is OK: computer port RS-485 works well with loopback, and controller do with his board also. So, I've tried two alternative pinouts for cable. I sent the correct commands into FR-A540, but it kept quiet. What's wrong?

[Crossbow]

You can use the RJ45 port. Mitsubishi makes a cable, SC-FRPC which connects from the RS485 RJ45 port to the PC RS32 port. RD would be receive data, SD would be send data. On the other end, RD is receive data and TC is transmit data. Cross them so SD connects to RD and RD to TD. A is positive and B is negative. This should all be covered in the A540 manuals.