S7-1200 Modbus RTU Error 8382

Having a problem and spent quite a bit time on that.

I can read whatever I want from this particular modbus device, but when I want to write 1 single bit to register 01015 (tried 1015), then I have error 8382.

Device supports commands 01 and 05. That means that if I select mode 1 on MB_Master, then I should be able to write 1 bit.

Try data address 41015.
Edit = 4xxxx is analog. Maybe 31015? I think you need long addresses (5 digit) for Siemens Modbus.

3xxxx and 4xxxx are occupied with other stuff and they are not bits. I read with no problems.

Can not write a bit

S7-1200 uses only 4xxxxx (holding) registers for modbus, AFAIK. So you'll have to work with that.
also it uses 4xxxxX instead of 4xxxx address range, as said earlier

So what you are saying TIA help file is not true?

I can read from Modbus device 01001-01016, 3XXXX, 4XXXX with no problem with S7 MB_MASTER mode 0

I can not write into single coil, which is located in address, which I could read. For example 01016.

I have tried to write TRUE, FALSE - I get 8382
I have tried to write 16#0000 and 16#FF00 and then i get 8382 and 8384.

I can not write data which I plan to put into 1016 into 41016, because in modbus device specs this holding register is occupied with other important stuff.

Does anyone have a print screen, which shows 101% working (at least for him) example how TIA handles 1 single coil writing?

Thanks

and this is how I read and get status with no problem

frzw said:

So what you are saying TIA help file is not true?

I can read from Modbus device 01001-01016, 3XXXX, 4XXXX with no problem with S7 MB_MASTER mode 0
Thanks

Click to expand...

Hmmm, I probably mixed single coil with single bit in holding register. I would trust TIA help file, not me.

As for write operation I would have to check help file on my laptop.