M580 input address starts at 1

Hi All,

We have a curious issue here.

Using Citect SCADA and M580 CPUs, firmware ver > 2.20

When Citect reads %M or %MW addresses, the bits are not offset, i.e. %M40 on SCADA = %M40 on the PLC.

However, for inputs %I or %IW, the address is offset by 1.

i.e. %I40 on SCADA = %I41 on PLC.

We are using MODNET30 for the SCADA driver and just "fixed" the issue by offsetting SCADA variable addresses by 1 - obviously not ideal.

In testing an older M580 with firmware v2.10 with the MODNET30 driver, everything works perfectly.

In the firmware release notes, there is a fix in v2.12 "Fix offset issue when M580 answering to Modbus FC02 and FC04 requests from SCADA". This release is from 2016.

So whatever this "fixed" firmware is doing, there does not seem to be a relevant driver for the new mapping - I have checked all the MODNET protocol differences and none of them match the address protocol of our M580s.

Has anyone come across this issue? If so, what was your solution?

tldr;
M580s return an offset address only when an input is read by Citect SCADA. %M and %MW work correctly.

Thanks in advance.