isolating a bit

[jimcav]

I am using rs logix 5000 with an l61 processor. i want to change the status of a single bit in a shift register without changing anything else.

thx jim cav

 

[DamianInRochester]

If you know exactly which bit you wish to change you can use the standard logic blocks with a mask.

For example, If you have an integer with bit pattern

1100 1100 1100 1111

and you just want to set bit #3,
Then just use an OR block with a mask of 0000 0000 0000 1000

 

[DamianInRochester]

Actually, I showed you the hard way.

All you really need to do is reference your tag at the bit level as a set or reset.

If you tag is a DINT named Cat

For example SET Cat.4

 

[TConnolly]

OTL DintTag.1

     DintTat.1

--------(L)--

Another way to do it (works well if the bit number is variable) CPT DintTag (DintTag OR 2**VAR) will set and CPT DintTag (DintTag AND NOT(2**VAR)) will clear.