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80C186EC/80C188EC Microprocessor User's Manual

80C186EC/80C188EC Microprocessor User's Manual

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INSTRUCTION SET DESCRIPTIONS<br />

Table C-4. Instruction Set (Continued)<br />

Name Description Operation<br />

DEC<br />

NOTE:<br />

Decrement:<br />

DEC dest<br />

Subtracts one from the destination<br />

operand. The operand may be a byte<br />

or a word and is treated as an<br />

unsigned binary number (see AAA and<br />

DAA).<br />

Instruction Operands:<br />

DEC reg<br />

DEC mem<br />

(dest) ← (dest) – 1<br />

The three symbols used in the Flags Affected column are defined as follows:<br />

– the contents of the flag remain unchanged after the instruction is executed<br />

the contents of the flag is undefined after the instruction is executed<br />

üthe flag is updated after the instruction is executed<br />

Flags<br />

Affected<br />

AF ü<br />

CF –<br />

DF –<br />

IF –<br />

OF ü<br />

PF ü<br />

SF ü<br />

TF –<br />

ZF ü<br />

C-12

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