Intel 80C188XL - Manual (Page 334)

C-11
INSTRUCTION SET DESCRIPTIONS
CWD Convert Word to Doubleword:
CWD
Extends the sign of the word in register
AX throughout register DX. Use to
produce a double-length (doubleword)
dividend from a word prior to
performing word division.
Instruction Operands:
none
if
(AX) < 8000H
then
(DX)
←
0
else
(DX)
←
FFFFH
AF –
CF –
DF –
IF –
OF –
PF –
SF –
TF –
ZF –
DAA Decimal Adjust for Addition:
DAA
Corrects the result of previously
adding two valid packed decimal
operands (the destination operand
must have been register AL). Changes
the content of AL to a pair of valid
packed decimal digits.
Instruction Operands:
none
if
((AL) and 0FH) > 9 or (AF) = 1
then
(AL) ← (AL) + 6
(AF)
←
1
if
(AL) > 9FH or (CF) = 1
then
(AL)
←
(AL) + 60H
(CF)
←
1
AF ü
CF ü
DF –
IF –
OF ?
PF
ü
SF ü
TF –
ZF
ü
DAS Decimal Adjust for Subtraction:
DAS
Corrects the result of a previous
subtraction of two valid packed
decimal operands (the destination
operand must have been specified as
register AL). Changes the content of
AL to a pair of valid packed decimal
digits.
Instruction Operands:
none
if
((AL) and 0FH) > 9 or (AF) = 1
then
(AL)
←
(AL) – 6
(AF)
←
1
if
(AL) > 9FH or (CF) = 1
then
(AL)
←
(AL) – 60H
(CF)
←
1
AF ü
CF ü
DF –
IF –
OF ?
PF
ü
SF ü
TF –
ZF
ü
Table C-4. Instruction Set (Continued)
Name Description Operation
Flags
Affected
NOTE: The three symbols used in the Flags Affected column are defined as follows:
– the contents of the flag remain unchanged after the instruction is executed
? the contents of the flag is undefined after the instruction is executed
ü the flag is updated after the instruction is executed