Hello

I've had some wierd behavior. Now I suspect, that the WV and V for coils and holding registers share the same memory on the LOGO! 8. Is this the case? Where can I find documentation for this?

Case is: I have some parameters that I read by modbus and have put them in the Parameters/VM list. Addidtionally I use some network inputs in the diagram. And they seem to change "randomly" when I run the software on the Logo but not in simulation.

could there be a collision in memory?

best regards, Marco

Hello,

VM memory is indeed shared and Coils vs HR reading is a matter of preference; accessing a "V" is just reading a bit in a specific "VW".

In LSC under any project in "Settings" -> "Modbus address space" the Modbus mapping clarifies that.

Thank you for the quick answer!

Anthing else that could pose a surprise? Are the AI registers (IR) mapped into the the HR and therfore VW as well?

Did you mean the attached table? This does not really clear it up for me that much but it gave me the idea thet there could be something. I'm probably lacking some pieces of basic understanding here. For me it was not obvious just from the Fact that both start with V and have the same "address range".

Some time ago i have made an own table and this you can find here and also in german conferences. This will show a little more as the Siemens table. Use 0 or 1 as start address of Modbus registers depend on your Modbus device. Logo e.g. starts all registers with 1 (coil, holding register, input register) Some Modbus devices starts with 0, then you need an offset in the Logo.

Regards, Scorp