Zilog Z80380 Manual do Utilizador descarregar pdf (Página 78)

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Z380

™

USER'S MANUAL

DC-8297-03

ZILOG

DEC

DECREMENT (BYTE)

DEC dst dst = R, RX, IR, X

Operation: dst ← dst – 1

The destination operand is decremented by one and the result is stored in the destination.

Two’s complement subtraction is performed.

Flags: S: Set if the result is negative; cleared otherwise

Z: Set if the result is zero; cleared otherwise

H: Set if there is a borrow from bit 4 of the result; cleared otherwise

V: Set if arithmetic overflow occurs, that is, if the destination was 80H; cleared otherwise

N: Set

C: Unaffected

Addressing Execute

Mode Syntax Instruction Format Time Note

R: DEC R 00-r-101 note

RX: DEC RX 11y11101 0010w101 2

IR: DEC (HL) 00110101 2+r+w

X: DEC (XY+d) 11y11101 00110101 ——d— 4+r+w I

Field Encodings: r: per convention

y: 0 for IX, 1 for IY

w: 0 for high byte, 1 for low byte

Note: 2 for accumulator, 3 for any other register

1 2 ... 73 74 75 76 77 78 79 80 81 82 83 ... 267 268

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Zilog Z80380 Manual do Utilizador Página 78