Obscure Controllogix timer status bits/flags?

[robertov]

In addition to the typical status bits of EN, TT, and DN, the Logix5000 Timer Tag shows additional status bits when viewed in Tag area.

Has anyone run across documentation that indicates what the conditions are that trigger these additional bits or how they might be used (aside from speculating)? (e.g. FS, LS, OV, ER)

Regards,
Bob

 

[RSL]

I have not used any of those bits before myself. Try the help button in Logix5000, instruction set reference. Detailed info on all instructions in it.

RSL

 

[Alan Case]

From the Rockwell Knowledge base.

Question:

RS5000 Help describes the TON, TOF & RTO timer instruction's .ACC, .EN, .TT and .DN bits but does not describe the .FS, .LS, .OV and .ER bits that are created in the timer tag as well. What are these bits and is there a practical use for them?

Answer:

These bits were added in anticipation of using timers with SFCs (Sequential Function Charts). At this time SFCs do not use timer structures so these bits are not used and are currently undefined.

Regards Alan Case

 

[RSL]

Thanks Alan, that answers that. I knew I had never used them before and ***umed they were in the help file.

RSL

 

[robertov]

From the Rockwell Knowledge base.

Question:

RS5000 Help describes the TON, TOF & RTO timer instruction's .ACC, .EN, .TT and .DN bits but does not describe the .FS, .LS, .OV and .ER bits that are created in the timer tag as well. What are these bits and is there a practical use for them?

Answer:

These bits were added in anticipation of using timers with SFCs (Sequential Function Charts). At this time SFCs do not use timer structures so these bits are not used and are currently undefined.

Regards Alan Case

Thanks... that's what I was looking for.

 

[rdrast]

In short... they are undocumented, DO NOT USE THEM.

 

[Operaghost]

They are not documented because they are not used. They don't DO anything. The infamous, for future use!


OG

 

[rdrast]

They don't do anything YET. Programmers doing software for computers always fall into the same ignorant trap... "Well, it's not documented, so I'm free to exploit it". Till the next OS upgrade, or even patch comes around.

Using bits like that in a PLC, IMHO, is about equivilant to shorting out and completely disabling all safety circuits on a press, and then getting a drunk operator to run it.

 

[robertov]

They don't do anything YET. Programmers doing software for computers always fall into the same ignorant trap... "Well, it's not documented, so I'm free to exploit it". Till the next OS upgrade, or even patch comes around.

Using bits like that in a PLC, IMHO, is about equivilant to shorting out and completely disabling all safety circuits on a press, and then getting a drunk operator to run it.

No one is advocating using them. The question regarded finding out what they were.

Give us some credit!