Allen Bradley B3 and #B3 bits

I was looking at a BSL instruction example and they used #B3:8 as an example for the file. Could you give me some information on adding the # sign to the B3 file. Also once I added the # sign could I use any other part of the B3:8 file like B3:8/0 any where else in the same program.

Hi Boyd Man,

The # sign tells it is the word address used by the shift address the length being one specified in the instruction. For eg, if #B3:8 is specified and length being 16 the shift register starts from bit address B3:8/0 to B3:8/15. It shifts a one when bit address in the BSL instruction is logically true and shifts a zero when the bit address is logically false.

You can make use of other part of the file to collect the status of the shifted bit or even unlatch it so the shifted status is changed from that address onwards

The # sign means that B3:8 is used as a file. B3:8/0 thru B3:8/15 if the length is set to 16.

The # indicates an indexed address (S:24 is the index register). The index register is manipulated by the bit shift instruction.

If the shift register length is not a multiple of 16 bits, then the unused bits in the end of the last word of the shift register should not be used as they will be over-written by the bit shift instruction.