CMP = Compare (8-Bits)

Hex Mnemonic Cycles
30 CMP A, A 8
31 CMP A, B 8
32 nn CMP A, #nn 8
33 CMP A, [HL] 8
34 nn CMP A, [N+#nn] 12
35 nn nn CMP A, [#nnnn] 16
36 CMP A, [X] 8
37 CMP A, [Y] 8
DB nn nn CMP [N+#nn], #nn 16
CE 30 ss CMP A, [X+#ss] 16
CE 31 ss CMP A, [Y+#ss] 16
CE 32 CMP A, [X+L] 16
CE 33 CMP A, [Y+L] 16
CE 34 CMP [HL], A 16
CE 35 nn CMP [HL], #nn 20
CE 36 CMP [HL], [X] 20
CE 37 CMP [HL], [Y] 20
CE BC nn CMP B, #nn 12
CE BD nn CMP L, #nn 12
CE BE nn CMP H, #nn 12
CE BF nn CMP N, #nn 12

Execute

#nn     = Immediate unsigned 8-Bits
#ss     = Immediate signed 8-Bits
A       = Register A
B       = Register B
N       = Register N
[N+#nn] = Memory: (I shl 16) or (N shl 8) or #nn
[HL]    = Memory: (I shl 16) or HL
[X]     = Memory: (XI shl 16) or X
[Y]     = Memory: (YI shl 16) or Y
[#nnnn] = Memory: (I shl 16) or #nnnn
[X+#ss] = Memory: (XI shl 16) or (X + #ss)
[Y+#ss] = Memory: (YI shl 16) or (Y + #ss)
[X+L]   = Memory: (XI shl 16) or (X + signed(L))
[Y+L]   = Memory: (YI shl 16) or (Y + signed(L))
    
; CMP Sc2, Sc
;
; Sc2 = Source 2
; Sc  = Source

(discarded) = Sc2 - Sc
    

Description

"8-Bits Source 2" subtracts with "8-Bits Source", result is discarded.

This instruction is used to compare values.

Conditions

Zero: Set when result is 0

Carry: Set when result is < 0

Overflow: Set when result overflow 8-bits signed range (< -128 OR > 127)

Sign: Set when bit 7 of the result is 1

Examples

; A = 0x55
CMP A, $80
; A = 0x55
;     0xD5 (0x55 - 0x80 = 0x(1)D4)
; F = (Zero=0):(Carry=0):(Overflow=1):(Sign=1)
    
; B = 0x31
; A = 0xCF
CMP A, B
; B = 0x31
; A = 0xCF
;     0x9E (0xCF - 0x31 = 0x(0)9E)
; F = (Zero=0):(Carry=0):(Overflow=0):(Sign=0)
    

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