John,


-----Original Message-----
From: John Albers <jalbers@GW.BSU.EDU>

<SNIP>

|However, things seem to get weird around 0, assume that W=0, after the
following is executed, I think that Carry flag should be zero. (maybe its
not, but I would like to know why)
|
|sublw       15
|
|According to the PIC16F84 data sheet, the sublw subtracts by using two
complement addition.  Therefore 15-0 = 15 + (Two's Complement of 0) = 15 +
(b'11111111' + b'1') = 15 + 0 = 15 which should not set the Carry Flag.
Carry Flag = 0 is supposed to imply that W > L, but W=0 and L=15 , and 0 is
NOT greater than 15.


I think You forget the carry bit produced when doing the 2's complement of 0
!

Best Regards,

S.-