First Howtos

Memory mapping

Any old-fashioned PLC consists on a predetermined memory mapping. I mean:

- any input or output is labelled as X, Y, IR, E, A, IX or QX;
- any internal mark or relay is labelled as M, MW, WR or others;
- any holding relay is labelled as HR;
- any register is labelled as MW, DM and so on;
- timers and counters are T, TIM, C, CNT, ...

What does it mean?

Arduino PLC-emulator could keep this same mapping. This could be done as arrays. This is quite helpful when working with communications in order to make things easier.