CYASM ASSEMBLER USER'S GUIDE VERSION 1.77

DEC Decrement DEC
Syntax:
Operation:
DEC A acc ← acc - 1
DEC X X ← X - 1
DEC [expr] [k] ← [k] - 1
DEC [X+ expr] [X+ k] ← [X+ k] - 1
Description:
Subtract one from the contents of a register or Data RAM location. The field to the right
of the opcode determines which entity is effected: accumulator; X register; direct or
index addressed Data RAM location.
Condition Flags:
CF:
ZF:
Set if the result is -1; cleared otherwise.
Set if the result is zero; cleared otherwise.
Source Machine Code Cycles
Format Opcode Operand
DEC A 25h 4
DEC X 26h 4
DEC [expr] 27h direct address byte 7
DEC [X+ expr] 28h offset address byte 8
DI Disable Interrupts DI
Syntax: DI B CPU only
Operation: None
Description:
Disables interrupts.
Condition Flags:
CF:
ZF:
Carry flag unaffected.
Zero flag unaffected
Source Machine Code Cycles
Format Opcode Operand
DI 70h 4
EI Enable Interrupts EI
Syntax: EI B CPU only
Operation: None
Description:
Enables interrupts.
Condition Flags:
CF:
ZF:
Carry flag unaffected.
Zero flag unaffected
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