Phases? RSLogix 5000

So I'm trying to understand equipment phases in RSLogix 5000 and am having some trouble conceptualizing their purpose.

Would it be fair to say that equipment phases are meant to control the machine in a broad sense? It would essentially issue general commands and then have other programs referenced to do the real work?

If this were the case, it seems like every equipment phase would then need to have a lot of regular programs accompanying them.

Also, I've read through the user's manual about switching states in a phase and how there are active and waiting states. The equipment phase only lets you add active states such as running, resetting, etc. Why can't you add an stopped or held state? It seems like you would need these states so you could insert a command in them to switch states (PCMD?).

I apologize if this is confusing to read, that's probably due to the fact that I'm extremely confused by it.

Hi look into batch 88

As cjd1965 has mentioned, the purposes of equipment phases stems from S-88, the industrial batching standard. If you read up on that you will better understand the philosophy and how it meshes with that standard.

Generally speaking though, equipment phases are not strictly for batch process'. We actually have standardized everything we do with equipment phases. All our projects resemble the same philosophy as S-88 (which can actually be applied just about anywhere) reguardless of if it is a batch or continuous process. If we need a step sequence, it will use an equipment phase.

Equipment phases have multiple states, and multiple commands that you can use. Because it is defined internally by Rockwell (to comply to S-88) many items are "standardized" for you. We add additional sub-routines to take care of sequence logic, error handling, and any unique code required. But typically 95% of the process logic is in the "Running" routine. From a maintenance perspective, if they simply look at the phase state, and the "running" routine logic they have a starting point for trouble-shooting. Which, is pretty intuitive, at least one would think.

A phase for us represents a specific process. We may have 1 single phase, or perhaps 200+ phases in our projects. Phases help create modular code, and phases help keep us organized. Sure we could create our own logic that works similar without using the official "Phase Manager" feature, but why do all the extra work?

Phases can be simple or complex. Phases could be completely independent, or they could have relationships. Really depends on the process you wish to accomplish.

Read the Phase Manager user's manual, should give you more detail on the inner-workings within the controller.