Intel 80287, 80286 manual Basic Instruction SET

BASIC INSTRUCTION SET

STATUS FLAGS:

CARRY -----------------------------------------------------------

,

PARITY -----------------------------------------------------

,

AUXILIARY CARRY ------------------------------------------

,

ZERO ---------------------------------

,

SIGN -----------------------------

,

1

OVERFLOW

t11

I

15

14

13 12

10

9

B

7

6

5

4 3 2 1 0

FLAGS: .

NT

Id."L

OF

I OF

I IF

I TF

I SF

I ZF

_

AF

1M PF _

CF

I

jlL_L

t_

TRAP FLAG

CONTROL FLAGS:

INTERRUPT ENABLE

' -------------------------------

DIRECTION FLAG

SPECIAL FIELDS:

' ------------------------------------------

I/O PRIVILEGE LEVEL

' ----------------------------------

' --------------

NESTED TASK FLAG

_

INTEL RESERVED

G3010B

Figure 3-5. Flag Word Contents

		Table 3-1. Status Flags'Functions
Bit Position	Name	Function
0	CF	Carry Flag-Set on high-order bit carry or borrow; cleared
		otherwise.
2	PF	Parity Flag-Set if low-order eight bits of result contain an
		even number of 1 bits; cleared otherwise.
4	AF	Set on carry from or borrow to the low order four bits of
		AL; cleared otherwise.
6	ZF	Zero Flag-Set if result is zero; cleared otherwise.
7	SF	Sign Flag-Set equal to high-order bit of result (0 if positive,
		1 if negative).
11	OF	Overflow Flag-Set if result is too-large a positive number
		or too-small a negative number (excluding sign-bit) to fit in
		destination operand; cleared otherwise.

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