57
D EC
D EC
DEC
REMENT BY ONE
(A)
←
(A) – 1, or
(M)
←
(M) – 1
This instruction subtracts 1 from the contents of A or M.
N is 1 when bit 7 is 1 after the addition; otherwise N is 0.
No change
No change
No change
No change
No change
Z is 1 when the operation result is 0; otherwise Z is 0.
No change
Op e r a t io n :
F u n c t io n :
St a t u s fla g :
Addressing mode
Accumulator
Zero page
Zero page X
Absolute
Absolute X
Machine codes
1A
16
C6
16
, zz
16
D6
16
, zz
16
CE
16
, ll
16
, hh
16
DE
16
, ll
16
, hh
16
Cycle number
2
5
6
6
7
Byte number
1
2
2
3
3
Statement
∆
DEC
∆
A
∆
DEC
∆
$zz
∆
DEC
∆
$zz,X
∆
DEC
∆
$hhll
∆
DEC
∆
$hhll,X
N :
V :
T :
B :
I :
D :
Z :
C :
