Modbus Communications address offset

[Beardsell]

Is there an option available in the Modicon Object to enable an address shift during communication with Modicon Devices.  When communicating with a Modicon Quantum PLC 400010 will return the value from the device in reg 400010 but when communication with a Modicon M340, Premium and others 400010 will return the value in 400009.

[Ryan.S]

We don't have such an option to shift the address.

The register address starts from 400001. What if you read address 400001 from Lookout?

[Beardsell]

400001 will return 400000.  Some Modbus devices are 0 based (Quantum) and others are 1 based (Premium, M340).  We can change the alias address to reflect the offset but I was looking for something simple.

[JimmyPage]

I am having the exact same issue, upgrading about 30 PLCs from TSX Compact to Modicon M340. Now every address I reference in every PLC I upgrade is going to be offset by one from the address I need? There has to be some solution somewhere.

[Mike@Forshock]

Nothing a little data member export and import cant fix...

On the standard Koyo (automationdirect) PLCs we have to convert from Octal to decimal, then add 1.  

For example:

PLC: V1200

Decimal: 640

MODBUS: 40641

[JimmyPage]

Finally found a solution deep in the M340 documentation. There are two system words, %SW139 and %SW141, that when put into the Data Editor and given a value allow the coil and register offset to be changed.

[RL74]

Just found this forum recently.

Upgrading from TSX Compact to M340. The code in the TSX uses memory bit %M to send data to SCADA. The existing SCADA uses 40000x addressing, somehow there is a correlation between %M and 40000x which I don't understand. I've replicated the %M address into the new M340 and used the existing addressing in the CitectSCADA, however does not work. There seem to be offset can figure out, even tried to offset by 1 in the PLC.

1. Do you just enter %SW139 and %SW141 in the data editor only or need to add it in the logic?

2. Do you know if there is a direct correlation between %M and modbus 40000x addressing? Does %M1 = 400001, or can %M1 = 401013.1 so on?

Need help I am totally lost and stuck on this problem.