User's Manual

THE 80286 INSTRUCTION SET
SUB-Integer Subtraction
Opcode
Instruction Clocks
28
Ir
SUB eb,rb
2,mem=7
29
Ir
SUB eW,rw
2,mem=7
2A
Ir
SUB rb,eb
2,mem=7
2B
Ir
SUB rW,ew
2,mem=7
2C
db
SUB AL,db
3
20 dw SUB AX,dw
3
80
15
db SUB eb,db
3,mem=7
81
15
dw SUB eW,dw
3,mem=7
83
15
db SUB eW,db
3,mem=7
FLAGS MODIFIED
Overflow, sign, zero, auxiliary carry, parity, carry
FLAGS UNDEFINED
None
OPERATION
Description
Subtract byte register from
EA byte
Subtract word register from
EA word
Subtract
EA byte from byte register
Subtract
EA word from word register
Subtract immediate byte from AL
Subtract immediate word from
AX
Subtract immediate byte from EA byte
Subtract immediate word from
EA word
Subtract immediate byte from
EA word
The second operand is subtracted from the first operand, and the first operand is replaced with the
result.
When a byte-immediate value
is subtracted from 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.
B-109