Nonworking Bits

Could someone clue me into the half dozen or so reasons that bits won't turn on in an RSLogix500 program.

For example; I:9/0 is true but the bit it is mapped to B31:0/0 remains false.

I seem to remember seeing this recently in another thread but I'm not having any luck finding it now.

Thanks

90% of the time the rung is in a file that is not being called.

the other 10% of the time the output bit is programmed elsewhere later in the program and is over Writing the value in the data table.

see if this helps ...

if you can manually "toggle" bit B31:0/0 to an ON condition, then the rung is probably not being scanned ... if the rung is in a file other than Ladder File #2, then you probably need a JSR (Jump to Subroutine) instruction in Ladder File #2 to tell the processor to scan your "problem" file ...

if you can NOT manually "toggle" bit B31:0/0 to an ON condition, then there is probably something else in your program (later in the scan) which is overwriting the status of B31:0/0 ... a "find all" search should help you find it ... post your code if you need more help ...

PS edit ... yeah ... just like Norm said while I was typing ...

Thanks guys, it was the 90% that got me this time. I hereby swear not to program in my sleep anymore. My productivity is probably going to go way down but these kind of mistakes aren't worth it.