THE
80286
INSTRUCTION SET
DEC-Decrement
by 1
Opcode
FE
/1
FF
/1
48+
rw
FLAGS MODIFIED
I!'structlon
DEC
eb
DEC
ew
DEC
rw
Clocks
2,mem=7
2,mem=7
2
Overflow, sign, zero, auxiliary carry, parity
FLAGS UNDEFINED
None
OPERATION
Description
Decrement EA byte by 1
Decrement
EA
word by 1
Decrement word register by 1
1
is
subtracted from the operand. Note that the carry flag
is
not changed
by
this instruction.
If
you
want the carry flag set, use the SUB instruction with a second operand of
1.
PROTECTED MODE EXCEPTIONS
#GP(O)
if the operand
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.
8-38
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