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BASIC INSTRUCTION SET
HIGH
ADDRESS
..
hm====i
OPERANDS
FROM
~n\\\\\\n\\l\~\\\\\\\
PREVIOUS
PUSH
INSTRUCTIONS
~\\\\\\\\\\\\\\\\\\\\\\\\
SP_
OPERAND
LOW
ADDRESS
Ok
BEFORE
POP
OPERAND
AFTER
POP
OPERAND
SS
,
POP
copies the
contents
of
the
slsck
location
before
SP
to
the operand In the Instruction.
POP
then Increments
SP
by
2
bytes
(1
word).
G3010e
Figure 3-3. POP
3.2
FLAG OPERATION WITH THE BASIC INSTRUCTION SET
3.2.1
Status Flags
The status flags of the FLAGS register reflect conditions that result from a previous instruction or
instructions. The arithmetic instructions use
OF, SF, ZF, AF, PF, and CF.
The
SCAS (Scan String), CMPS (Compare String), and LOOP instructions use
ZF
to signal that their
operations are complete. The base architecture includes instructions
to
set, clear, and complement
CF
before execution of an arithmetic instruction. See figure
3-5
and tables
3-1
and
3-2.
3.2.2
Control Flags
The control flags of the FLAGS register determine processor operations for string instructions, maska-
ble interrupts, and debugging.
3-4