Since the piclist is back down to only 50 messages or so a day,
I figured it was time to throw another bit-banging challenge out
there. This is very similar to the the bit-ANDing one I threw out
a few weeks ago.

This time the goal is to exclusive-or two bits.

Given:
 bit_a  of register A
 bit_b  of register B
 bit_c  of register C

The goal in C parlance is:

  C.bit_c = A.bit_a ^ B.bit_b;

  A.bit_a   B.bit_b  | C.bit_C
---------------------+---------
    0          0     |   0
    0          1     |   1
    1          0     |   1
    1          1     |   0



Here's a reasonably slow version to get you started:

      CLRW             ;and set Z (i.e. result is zero)
      BTFSC   A,bit_a  ;If A.bit_a is high
       XORLW  1        ; then W=1 and clear Z

      BTFSC   B,bit_b
       XORLW  1

      SKPZ             ;If the above was non-zero
       BSF    C,bit_c  ; then set C accordingly
      SKPNZ            ;otherwise
       BCF    C,bit_c  ; clear C



Let's optimize the speed vector:

  points = 9 - max execution cycles

My best version scores 3 points.



Scott

PS. Andy, I'll give you back the beer if you can score
4 points or buy you a bud lite if you score 3.