Intel 80286, 80287 manual ADC/ ADD-Integer Addition, Adc

THE 80286 INSTRUCTION SET

ADC/ ADD-Integer Addition

Opcode			Instruction		Clocks	Description
10	Ir		ADC	eb,rb	2,mem=7	Add with carry byte register into EA byte
11	Ir		ADC	eW,rw	2,mem=7	Add with carry word register into EA word
12	Ir		ADC	rb,eb	2,mem=7	Add with carry EA byte into byte register
13	Ir		ADC	rW,ew	2,mem=7	Add with carry EA word into word register
14	db		ADC	AL,db	3	Add with carry immediate byte into AL
15	dw		ADC	AX,dw	3	Add with carry immediate word into AX
80	12	db	ADC	eb,db	3,mem=7	Add with carry immediate byte into EA byte
81	12	dw	ADC	eW,dw	3,mem=7	Add with carry immediate word into EA word
83	12	db	ADC	eW,db	3,mem=7	Add with carry immediate byte into EA word
00	Ir		ADD	eb,rb	2,mem=7	Add byte register into EA byte
01	Ir		ADD	eW,rw	2,mem=7	Add word register into EA word
02	Ir		ADD	rb,eb	2,mem=7	Add EA byte into byte register
03	Ir		ADD	rW,ew	2,mem=7	Add EA word into word register
04	db		ADD	AL,db	3	Add immediate byte into AL
05	dw		ADD AX,dw		3	Add immediate word into AX
80	10	db	ADD	eb,db	3,mem=7	Add immediate byte into EA byte
81	10	dw	ADD	eW,dw	3,mem=7	Add immediate word into EA word
83	10	db	ADD	eW,db	3,mem=7	Add immediate byte into EA word

FLAGS MODIFIED

Overflow, sign, zero, auxiliary carry, parity, carry

FLAGS UNDEFINED

None

OPERATION

ADD and ADC perform an integer addition on the two operands. The ADC instruction also adds in the initial state of the carry flag. The result of the addition goes to the first operand. ADC is usually executed as part of a multi-byte or multi-word addition operation.

When a byte immediate value is added to a word operand, the immediate value is first sign-extended.

PROTECTED MODE EXCEPTIONS

#GP(O) if the result is in a non-writable segment. #GP(O) for an illegal memory operand effective address in the CS, DS, or ES segments; #SS(O) for an illegal address in the SS segment.

REAL ADDRESS MODE EXCEPTIONS

Interrupt 13 for a word operand at offset OFFFFH.

8-19