Zilog Z16F2810 Manual do Utilizador descarregar pdf (Página 165)

UM018809-0611 SBC Instruction

ZNEO

CPU Core

User Manual

149

SBC

Definition

Subtract with Carry

Syntax

SBC dst, src

Operation

dst  dst

– src – C

Description

This instruction subtracts the source operand and the Carry (C) flag from the destination. The

result is stored in the destination address or register. The contents of the source operand are unaf-

fected. The ZNEO CPU performs subtraction by adding the two’s-complement of the source

operand to the destination operand. This instruction is used in multiple-precision arithmetic to

include the carry (borrow) from the subtraction of low-order operands into the subtraction of

high-order operands.

The Zero flag is set only if the initial state of the Zero flag is 1 and the result is 0.

This instruction is generated by using the Extend prefix, 0007H, with the SUB opcodes.

Flags

76543210

C Z S V B CIRQE IRQE

*****–––

Legend

C = Set to 1 if the result generated a borrow; otherwise set to 0.

Z = Set to 1 if Z is initially 1 and the result is zero; otherwise set to 0.

S = Set to 1 if the result msb is 1; otherwise set to 0.

V = Set to 1 if an arithmetic overflow occurs; otherwise set to 0.

B = Set to 1 if the initial destination or source value is 0; otherwise set to 0.

CIRQE = No change.

IRQE = No change.

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