Mitsubishi FX2N download with GX Developer

We buy and sell used industrial machinery. We have a machine with a Mitsubishi FX2N 32MR-ES/UL PLC. The battery light was on when we first powered it up and sure enough, the program was lost. We sent the PLC back to the manufacturer to be reprogrammed. When it was returned, I got an upload (as we try to do with every (PLC) machine that arrives).

However, when we reinstalled it, there was no communication with the HMI. We've tested the HMI on another machine and it works fine. We've examined and "belled out" the cable and all seems fine there. So I would estimate it's 90%+ that the PLC is defective or its settings are wrong.

Speaking with the machine manufacturer, they said that:

"The internal memory of the PLC needs to be cleared before updating the program and I do it with all PLC software uploads [I think he means downloads]. I had another similar incident a few years back where the PLC needed to be reprogramed for similar issues."

Is this a thing with FX2Ns? I see the Clear PLC Memory button in the Write to PLC dialog in GX Developer. I assume that's what I need to click before I download the program that I uploaded? What's the likelihood that the upload is defective do you think? I'm going to try it anyway - the machine manufacturer has offered to reprogram it again for free anyway. Just trying to save some time and carriage costs.

First of all can you connect via a pc & interface with GX developer or what ever programming software you use. Secondly is the HMI on a separate port to the programming port i.e. FX422BD board & what HMI is it.
There are a number of causes if it is on a second port it may be that the com settings are wrong in the plc parameterisation and they have not downloaded them . If it's a Beijers on the main port it should not make any difference as these can get the PLC to change it's Baud rate on the fly.

Thanks for the reply.

Yes, we can connect - we were able to get an upload using GX Developer v8.102G.

The Pro-face GP270-SC21-24VP HMI connects via an FX2N-232-BD plugged into the front and the programming PC plugs in to the 8-pin mini DIN.

Then I suspect that the BD board has not had it's settings changed I bet they have not downloaded the plc parameters I would check with the supplier I'm not familiar with the proface so it may not use the programming protocol I cannot remember but Some people set the D8120 register (I think) which sets the protocol on the BD board. I would definitely check with the supplier.
Normally if they change the settings then they will set a hex value using M8002 (on first scan) to load a hex value to D8120, however I have seen where they just force the register via the PC, if you loose battery it will reset back to 0

Just as a matter of interest, The FX 2N & that HMI are no longer supported, however, there is a direct replacement for the FX2 & that's the FX3U just thought I would let you know.

Good news! I got it working! Your comments put me on the right track, so thank you. I had to enable the comms on port 2 and set the parameters to match the HMI.

Just as a matter of information you can do this programmatically in the ladder
This way if ever the plc loses it's program so you don't have to re-load the parameters (not that it makes much difference to be honest) at the start of the ladder you have the one scan flag (M8002 on for one scan only) move a hex value to D8120
So AND M8002 [Mov H6082 D8120] the Hex value sent to D8120 (communications parameter) is composed of bit patterns in the 16 bit word this determines things like baud, parity etc. (SWee FX communications manual).