Allen-Bradley Inputs

I'm looking at Micrologix PLCs and I've got a question about the input types.

Does anyone know what the 'Fast' means in AB's fast 24 VDC FET input?

I think I'm going to order the Micrologix 1100 1763-L16BBB, which has two 'fast' and two regular FET inputs. I'm just curious as to what that means before I actually place my order. The AB website hasn't been a great resource for me.

They can be used for high speed interrupts, which is set within the PLC's program.

I believe the current FW versions are 40kHz fast.

I think you are mixing up terms for the inputs and outputs. See attached.

Whoops, yeah I accidentally had the FET in there.

OK, so this is just an added benefit? As in the fast inputs can be used for regular applications but can also be for high speed interrupts if necessary.

Get the reference and user manuals for more information.

Yes, I've looked at both of those documents and maybe I'm blind but I can't find anything explicit that says that the 'fast' inputs are essentially backwards compatible to 'not fast' inputs.

I don't need the fast capability and would like to make sure I'll have enough regular, for lack of a better term, inputs.

Yes they will be fine.

If you can RUN then you can probably WALK also.

In RSLogix500, once you have the 1100 selected as the controller, go to 'I/O Configuration'. Click in the CPU then choose the 'Adv Config' button.

Under the 'Embedded General Configuration' tab choose 'BBB Base' as the base. Then choose the 'Embedded I/O Config' tab. Here you can set the input filtering. Leave them at 'default' for standard (limit switch or prox for example) inputs. You will probably want to choose a much shorter filtering time for a high speed (encoder for example) application. I choose about 1/10th of the shortest pulse which will appear at the input.

In the Reference Manual use the chapter titled 'Using the High-Speed Counter and Programmable Limit Switch' for information on configuring the Function Files for this use.

Haha yes, I thought that being able to walk was most likely the case, I just wanted to verify before I spend money on something I clearly don't know much about.

Thanks again to everybody for helping this novice out.