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C-41
INSTRUCTION SET DESCRIPTIONS
SBB Subtract With Borrow:
SBB
dest, src
Subtracts the source from the desti-
nation, subtracts one if CF is set, and
returns the result to the destination
operand. Both operands may be bytes
or words. Both operands may be
signed or unsigned binary numbers
(see AAS and DAS)
Instruction Operands:
SBB reg, reg
SBB reg, mem
SBB mem, reg
SBB accum, immed
SBB reg, immed
SBB mem, immed
if
(CF) = 1
then
(dest) = (dest) – (src) – 1
else
(dest) ← (dest) – (src)
AF
CF
DF –
IF –
OF
PF
SF
TF –
ZF
Table C-4. Instruction Set (Continued)
Name Description Operation
Flags
Affected
NOTE: The three symbols used in the Flags Affected column are defined as follows:
– the contents of the flag remain unchanged after the instruction is executed
? the contents of the flag is undefined after the instruction is executed
the flag is updated after the instruction is executed