Slc Logic Help

[bernie_carlton]

Gmferg is correct (patting each other's back). The search has no idea what the value of the indirect will be at runtime. It could be anything within the range of the data table. Should it show all possible bits as used?

Check every use of indirects which reference the B3 data table. Start with anything starting with B3:5 for indirect bits. Then B3 with indirect words. You may find something. It may be a long exercise in nothing. Or it may be a lesson in blindly taking the next available suggestion from RSLogix.

 

[Lancie1]

Kid,

Bernie's solution is the most probable. Somewhere in your program, there probably is an insruction that is writing a value to B3:5 (16-bit word), which will include your bit, and resets it to 0.

Your bit could be over-written by many different instructions that use Indirect-addressing, or even by such program instructions as COP (Copy File) which can copy values into a large series of memory words, or FLL (File Fill) which will copy a value into many 16-bit words.

None of these will necessarily show up in a search, or as a "used address".

An easy fix is to use a different bit for your seal-in!

Why will search not pickup indirects?

This PLC is not yet "smart" enough. Maybe someday...

What about the usage screen? Will it show indirects as used?

Unfortunately, it will not. I have learned this over and over, the hard way!

I typically let logix auto assign the next unused bit so in doing this is it possible for logix to assign a bit that is used as an indirect?

Yes! Yes!

If it has no way to find indirects, how would it know not to auto assign a particular bit?

It doesn't!

PS: You did "verify" the rung after you did your editing, didn't you?

 

[leitmotif]

Nope i check the tag Db in the easytouch panel that it is connected to. No tags with that address used or unused.

The address is not used anywhere else in the plc program.

As long is i hold the silence/ack pb or force it on the circuit works correctly and silences the horn. but it will not seal itself in.

Maybe i can get the boss to let me post the .rss with no comments. Would that help? I just don't know what else to check.

my boss seems to thing i set it up wrong.He thinks just because i am 18 that i can't know what i am doing.I am glad to hear that it is not a rookie mistake. I have been second guessing myself all day. Thanks

Schematic as shown looks good to me the alarm silence portion i believe is correct. What I wonder is - is the float switch resetting too quick?

I agree with Bernie. Most of my problems like this were caused either by typos or assigning the same bit value to two different actions. Pullled a few hairs finding my own dumb mistakes. Hard copy your logic and go thru with red pen for every b 3 5 15 to make sure no duplicates by error.

Dan Bentler