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THE
80286
INSTRUCTION SET
SBB-Integer
Subtraction With Borrow
Opcode
Instruction Clocks
18
Ir
SBB eb,rb
2,mem=7
19
jr
SBB eW,rw
2,mem=7
1A
Ir
SBB rb,eb
2,mem=7
1B
Ir
SBB rW,ew
2,mem=7
1C
db
SBB AL,db
3
10
dw
SBB
AX,dw
3
80
13
db
SBB eb,db 3,mem=7
81
13
dw
SBB eW,dw 3,mem=7
83
13
db
SBB eW,db
3,mem=7
FLAGS MODIFIED
Overflow, sign, zero, auxiliary carry, parity, carry
FLAGS UNDEFINED
None
OPERATION
Description
Subtract with borrow byte register from
EA
byte
Subtract with borrow word register from
EA
word
Subtract with borrow
EA
byte from byte
register
Subtract
with
borrow
EA
word
from word
register
Subtract with borrow imm. byte from AL
Subtract with borrow
imm.
word
from
AX
Subtract with borrow
imm.
byte from
EA
byte
Subtract with borrow
imm.
word from
EA
word
Subtract with borrow imm. byte from
EA
word
The second operand
is
added to the carry flag and the result
is
subtracted from the first operand. The
first operand
is
replaced with the result of the subtraction, and the flags are set accordingly.
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-99