Difference between revisions of "PM Opc DEC"
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(Join 8 and 16 bits of DEC) |
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; [N+0x88] = 0xFF | ; [N+0x88] = 0xFF | ||
− | ''' | + | '''DEC [N+$88]''' |
; [N+0x88] = 0xFE (0xFF - 1 = 0xFE) | ; [N+0x88] = 0xFE (0xFF - 1 = 0xFE) | ||
; F = (Zero=0) | ; F = (Zero=0) |
Revision as of 00:27, 21 April 2009
DEC = Decrease Register by 1
Hex | Mnemonic | Cycles |
---|---|---|
88 | DEC A | 8 |
89 | DEC B | 8 |
8A | DEC L | 8 |
8B | DEC H | 8 |
8C | DEC N | 8 |
8D nn | DEC [N+#nn] | 16 |
8E | DEC [HL] | 12 |
8F | DEC SP | 8 |
98 | DEC BA | 8 |
99 | DEC HL | 8 |
9A | DEC X | 8 |
9B | DEC Y | 8 |
Execute
A = Register A B = Register B L = Register L H = Register H N = Register N SP = Register SP (Stack Pointer) BA = Register BA: (B shl 8) or A HL = Register HL: (H shl 8) or L X = Register X Y = Register Y [N+#nn] = Memory: (I shl 16) or (N shl 8) or #nn [HL] = Memory: (I shl 16) or HL
; DEC Ds ; ; Ds = Source/Destination Ds = Ds - 1
Description
"Destination" is decremented by 1.
Conditions
Zero: Set when result is 0
Carry, Overflow and Sign remain unchanged
Examples
; A = 0x55 DEC A ; A = 0x54 (0x55 - 1 = 0x54) ; F = (Zero=0)
; [N+0x88] = 0xFF DEC [N+$88] ; [N+0x88] = 0xFE (0xFF - 1 = 0xFE) ; F = (Zero=0)
; BA = 0x2997 DEC BA ; BA = 0x2996 (0x2997 - 1 = 0x2996) ; F = (Zero=0)
; X = 0xFFFF DEC X ; X = 0xFFFE (0xFFFF - 1 = 0xFFFE) ; F = (Zero=0)