Hi Guys,

I have a very basic question about the 'RRF' command, for a program using a 16F627.

I am using RB1,2,3,4 to read a DIP switch to choose 1 of 16 different outcomes. (RB0 is being used as an external interrupt otherwise it wouldn't be a problem)

I want to read the switch  ...  'RRF' the result to scrub off the least significant bit  ...  then use that result (a number between 1 - 16 ) to offset the program counter etc.

I'm not sure of what I can 'operate' on  ...

Can I use  ...

      rrf           portb,w             ; remove the least sig bit

... or does that mess with portb as well ... which has actual switches on it. Then  ...

     andlw      b'00001111'     ; only keep the 4 lowest bits
     addwf      pc,f                   ; add offset to prog counter


...  or do I have to read the port, move it into a seperate file register ..  'RRF' that  ...   then move the result into 'w' to offset the program counter ?

...  or alternatively, can I 'RRF'  'W' and put the result in 'W' ?

I would have assumed the last one would be possible, but I cant find any examples of it, so have been wondering.

Thanks for any help.

Regards,   Roger

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