What's the point of different series cards and tell me about compatability

Hello Everyone.

I know with Rockwell stuff, the series card is important, cant' just swap a series A input card with a serB, even if the catalog number is identical.

Is this always the case with AB?

Why do they have different series?

Welcome to the PLCTalk forum community !

In general, A-B Series letters describe either a significant change in functionality or a significant change in hardware, or both.

Unfortunately, you need to know the details to find out if the change affects backward compatibility or not.

For example, the venerable 1771-IFE analog input module for the PLC-5. The Series C changes both added functionality (over/under range) and moved to new hardware. There's a compatibility jumper on the top of the module that lets it run identically to Series A and B.

A different example is the 1756-L61 controller. Series B controllers have a different main board hardware layout and some new components. The CF card slot moved to the front of the controller and the RS-232 port changed positions and the memory backup battery is slightly different and has a different plug.

But from a firmware, performance, and compatibilty perspective, an 1756-L61 Series A and Series B controller are identical. RSLogix 5000 can't tell the difference.

Some manufacturers do this differently. Some change the part number, article number or other designator entirely. Some don't change anything and rely on a firmware revision or serial number to distinguish between functional versions of a device.