Category:Z80 Assembly: Difference between revisions
m
→Flags
Puppydrum64 (talk | contribs) m (→Bit Shifting) |
Puppydrum64 (talk | contribs) m (→Flags) |
||
Line 28:
* Zero flag = equals 1 when the last math operation resulted in a 0, and equals 0 if not. Note that loading a zero (or any value really) into a register does NOT affect this flag, which is not the case for every CPU out there.
* Carry flag = equals 1 if the last math operation generated a carry or borrow (essentially a rollover from $FF to $00 or vice versa.) For comparisons, if Accumulator < Operand, carry is set. If Accumulator >= operand, carry clear. The carry can be set manually with <code>SCF</code>, flipped with <code>CCF</code>, or cleared with <code>OR A</code>.
* Parity/Overflow flag = this flag can represent either Bit Parity or Signed Overflow depending on what instruction was executed last. For arithmetic instructions like ADD and SUB, this represents whether a signed overflow occurred (essentially a rollover from $7F to $80 or vice versa.) For bitwise operations, this flag equals 1 if there are an even number of 1s in the byte, and 0 otherwise. The Game Boy does not have this flag.
| |||