THE
80286
INSTRUCTION SET
PUSHF-Push
Flags
Register onto the Stack
Opcode Instruction Clocks Description
9C PUSHF 3
Push
register
FLAGS MODIFIED
None
FLAGS UNDEFINED
None
OPERATION
The stack pointer
SP
is
decremented
by
2,
and the 80286 flags register
is
copied
to
the
new
top of
stack, which
is
pointed to
by
SS:SP. The flags, from the top bit (15)
to
the bottom bit (0), are as
follows: undefined, nested task,
I/O
privilege level
(2
bits), overflow, direction, interrupts enabled,
trap, sign, zero, undefined, auxiliary carry, undefined, parity, undefined, and carry.
PROTECTED MODE EXCEPTIONS
#SS(O)
if the
new
value of
SP
is
outside the stack segment limit.
REAL ADDRESS MODE EXCEPTIONS
None; the 80286
will
shut
down
if
SP=
I
due-to
lack of stack space.
8-89
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