User's Manual

BASIC INSTRUCTION SET
STATUS FLAGS:
CARRY-----------------------------------------------------------,
PARITY -----------------------------------------------------,
AUXILIARY CARRY ------------------------------------------,
ZERO ---------------------------------,
SIGN -----------------------------, 1
OVERFLOW I
15 14 13 12 t 11 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
_t _ CONTROL FLAGS:
L ______________________ TRAP FLAG
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.
3-6