PM Opc SAR

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Revision as of 03:55, 19 April 2009 by JustBurn (talk | contribs) (SAR Instruction)
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SAR = Shift Arithmetic Right

Hex Mnemonic Cycles
CE 88 SAR A 12
CE 89 SAR B 12
CE 8A SAR [N+#nn] 20
CE 8B SAR [HL] 16

Execute

A       = Register A
B       = Register B
[N+#nn] = Memory: (I shl 16) or (N shl 8) or #nn
[HL]    = Memory: (I shl 16) or HL
; SAR Ds
;
; Ds = Source/Destination

Ds = (Ds AND 0x80) OR (Ds SHR 1)

Description

"8-Bits Destination" bits are arithmetically shifted right by 1.

NOTE: This instruction can be used as an signed integer division by 2.

Conditions

Zero: Set when result is 0

Carry: Set when the old bit 0 was 1

Overflow: Always Reset (there's never a overflow)

Sign: Set when bit 7 of the result is 1

Examples

; A = 0x04 (4)
SAR A
; A = 0x02 (2)
; F = (Zero=0):(Carry=0):(Overflow=0):(Sign=0)
; A = 0xFD (-4)
SAR A
; A = 0xFE (-2)
; F = (Zero=0):(Carry=0):(Overflow=0):(Sign=1)
; B = 0x45 (69)
SAR B
; B = 0x22 (34)
; F = (Zero=0):(Carry=1):(Overflow=0):(Sign=0)
; B = 0x84 (-124)
SAR B
; B = 0xC2 (-62)
; F = (Zero=0):(Carry=0):(Overflow=0):(Sign=1)
; [HL] = 0x01 (1)
SAR [HL]
; [HL] = 0x00 (0)
; F = (Zero=1):(Carry=1):(Overflow=0):(Sign=0)

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