Mitsubishi A1SJ71UC24-R4 and Intouch?


Thread Starter

Mark Hellyer

Looking for some advice and encouragement on setting up an A1S comms module on RS485, using MELSEC A with InTouch SCADA.

On the module - I have the RUN led ON, the CPU led ON (but not flashing as the manual states?). The Rx led flashes when I request data but nothing comes back.

The PLC contractor reckons the module and PLC are OK - but they also have a RS232 module in another slot(communicating to another A1S) - is this module taking all the A1S resources?

Also the module has a 'computerlink' mode and an 'multi-drop' mode, and I have conflicting opinions on what I should/could use? Personally I can't see much difference?
Hi Mark! I posted a reply here before with the person with the same problem as yours. The complexity of setting up the configurations is
sometimes a burden. I have tried this system two years ago, A1S with InTouch and they're quite compatible as long as you configure all settings correctly. Check the baudrate and its settings (parity, stop bits, etc.). Don't rely on the manual for defaults. Sometimes, it's different. Also, if you are using an RS-485 from the PLC comm module, you need an RS-232 to RS-485 converter because a PC can only communicate through RS-232. Check your wires for twists. I mean, Rx should always go to the Tx. Double check (and check again). In order to get a partial data, your IOServer (Melsac A) should be running. The configuration inside this driver should all correspond to the one you set (especially the baud rate). Also, you should run InTouch and probably link some addresses (just one will be enough) in order to introduce a communication. If all's well, your Rx/Tx in the converter should be blinking, and you can also see "LIVE" addresses inside the Melsec A IOServer (based on what you configured in your InTouch).
Thanks for your reply Ting.

Did you use two wire or four wire RS485?

The Mitsubishi manual suggests either, but I cannot see how you 'tell' the module which way its wired so the ouputs/inputs now how to work!

That is, there is know two-wire/four-wire switch?

We have been trying four wire to date.