Term for this "BIT" 1

[dydt]

in troubleshooting or debugging on-line i always select a bit to block or disable a rung temporarily until i got my investigation or troubleshooting done...my question is ...is there a universal term for this "BIT" that i can use to communicate with other programmers or technicians?

thanks
dydt

 

[SteveMeisel]

We like to use the first available bit (b3/0 if it hasn't already been used) and unlatch it unconditionally on the first rung. Use "ALWAYS FALSE" for the description. When it is stuck on the first rung it is the first thing shown when going on-line. I have seen other programmers do the same thing using the same description. Sure this may cause problems if somewhere in the code someone accidently uses it as a coil but if they pay attention to the description it won't happen. Then when doing some troubleshooting just stick an "always false" bit in. Anyways it works just fine for us.

 

[tomatge]

Depending upon which PLC you're using, there is likely to be such a bit defined in the system. On GE Fanuc PLC's, there is an "ALW_OFF" bit (or conversely an "ALW_ON&quot.

 

[Wattman]

I have ran across this in programs written by others alot, and it has been refered to as a DUMMY bit and maybe any Bit address.

Works for me

 

[CasterJack]

If you're using something like AB RSLogix you can name your bit and add some pretty lengthy verbage as a description to avoid any confusion. (bitname "SCRATCH_BIT" and description "TOGGLE BIT FOR DEBUGGING 11/12/02" for example).

 

[rsmpls]

"AB" has an "AFI" (Always False Instruction)I just insert it and test edits. Works great and can not be mistakenly toggled high.

 

[skills]

If you were using Direct Logic stuff you would use _off to disable rung. to enable or bypass, you use _on. I hope this
helps. I communicate this to my engineers by saying set False and set True. In symbolic programming everyone would get the idea quite apart from the syntactic mechanism.

We write systems with tybacks, features that may never be utilized in said implementation, and this is how we code them for readability.