1) Dec (B) - Hitachi H8/300H Series Programming Manual

2.2.25 (1) DEC (B)

DEC (DECrement)
Operation
Rd – 1 → Rd
Assembly-Language Format
DEC.B Rd
Operand Size
Byte
Description
This instruction decrements an 8-bit register Rd (destination register) and stores the result in the
8-bit register Rd.
Available Registers
Rd: R0L to R7L, R0H to R7H
Operand Format and Number of States Required for Execution
Addressing
Mnemonic
Mode
Register direct DEC.B
Notes
An overflow is caused by the operation H'80 – 1 → H'7F.
Condition Code
H: Previous value remains unchanged.
N: Set to 1 if the result is negative; otherwise
Z: Set to 1 if the result is zero; otherwise
V: Set to 1 if an overflow occurs (the
C: Previous value remains unchanged.
Operands
1st byte
Rd 1 A
79
I UI H U
— — — —
cleared to 0.
cleared to 0.
previous value in Rd was H'80);
otherwise cleared to 0.
Instruction Format
2nd byte 3rd byte
0 rd
Decrement
N Z V C
—
No. of
States
4th byte
2