> What I want to happen is this:
> 
> 11111111
> 01111111
> 10111111
> 11011111
> 11101111
> 11110111

I tried this in MPLAB

         movlw   0xff
         movwf   temp_var
         clrc
main     nop
         movf    temp_var,w
         rrf     temp_var
         goto    main

and do get what you want - a rotating 0. clrc before 'main'
guarantees this. If you don't use clrc it's 50:50, depending on
the status of C before you start. Effectively you have a 9-bit
shift register, and if all bits are 1, they'll stay 1, no matter how
many rotates you do

I have absolutely no idea how you get this

11111111
01111111
10000000
11000000
11000001
11100001
11100010

Something else is going on. It doesn't appear to be random,
but it's not entirely a repeating shift effect either

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