AB : Controllogic

What is the relationship between I/O Memory and Data and Logic Memory.

I/O Memory is the amount of physical I/O addressing space the Processor can support, and can change based on the CPU.

"Data and Logic Memory" is the amount of memory available for, well, uhhh.. 'Data and Logic'. That is, tags you create, program code, UDT Definitions and instances, etc. It's base size depends on the memory module attached to the processor.

Am I correct in assuming that the memory size (ie. 3.7 or 7Mb) of the PLC (same CPU) will not have an effect on the I/O memory.

Yes, that is correct.

You can verify this yourself, if you have RSLogix5000 Version 13 and up. Create a project, select a processor, then go go the "Memory" tab on the CPU Properties and try changing the memory module from the drop-down.

Thank You