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DEY
(Y) – $0001 ⇒ Y
Operation:
Description:
Subtract one from index register Y. LEAY –1,Y can produce the same
result, but LEAY does not affect the Z bit. Although the LEAY instruction
is more flexible, DEY requires only one byte of object code.
Only the Z bit is set or cleared according to the result of this operation.
Condition Codes and Boolean Formulas:
S
–
Z:
Addressing Modes, Machine Code, and Execution Times:
Source Form
DEY
CPU12
REFERENCE MANUAL
Decrement Index Register Y
X
H
I
N
Z
∆
–
–
–
–
Set if result is $0000; cleared otherwise.
Address Mode
INH
INSTRUCTION GLOSSARY
V
C
–
–
Object Code
03
DEY
Cycles
Access Detail
1
O
MOTOROLA
6-77
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