RS logix 500 B3 memory bit

[Stuwertz]

Hi all ,

Thanks for this forum so far I got support from this forum .

In rs logix 500 program B3:30/0, B3:30/1 internal memory bits used . I try to find this bit referring which output. I checked in cross reference this OTE bit not available.i checked with hmi tags also not able to found . I don’t have this programs original back up . So I don’t have any rung command and description also . I worked in rs logix 5000. But in 500 I’m not familiar.

Could someone explain this scenario.

 

[OkiePC]

B3:30 is a sixteen bit word (integer). B3 is the file name. 30 is the element number within that file. B3:30/0 is bit zero within that 16 bit word. B3:30/1 is bit number one within that word.

With RSLogix 500, you can use the right click menu to "Find All" and get a resulting list that will let you navigate to every usage of that exact address BUT...

If the address is operated on at the word level (something is writing to all 16 bits of B3:30) then you may need to Find All with the address entered to the word level.

On top of all that, there are instructions that can write to multiple words, so this is where the Usage feature is handy. If you open up the Data Table for B3 and click the Usage Button you will see X on addresses that are in use. This requires you to enable the cross reference feature in your software options. You can enable this feature for online and offline operations separately.

Depending on the data table radix view (Binary, showing all the bits with the words in a list; or Element Only, showing all the words in a grid) you may also see other indicators for Usage, like "F" and "W". Those indicate File and Word level usage respectively.

If the Usage just shows a "." for that address, then it is not being utilized by the PLC logic directly. That STILL leaves two possible ways it could be changing.

Indirect addressing, and external communications.

Indirect addressing is less common than having an HMI or another PLC reading and writing to it, so the latter is where to look next.

Hopefully this gets you started.