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INSTRUCTION SET
CPL
FO
Complement
Flag
0 (Not in 8021,8022)
11001101011
The setting
of
flag 0 is complemented; one
is
changed
to
zero, and zero is changed
to
one.
FO
....
NOT
(FO)
CPL
F1
Complement
Flag
1 (Not in 8021,8022)
11011101011
The setting
of
flag 1 is complemented; one is
changed
to
zero, and zero is changed
to
one.
(F1)--
NOT
(F1)
DA A Decimal
Adjust
Accumulator
1
0101
101111
The 8-bit
accumulator
value is adjusted
to
form
two
4-bit Binary Coded Decimal (BCD)
digits
following
the binary addition
of
BCD numbers. The carry bit
C is affected.
If
the contents
of
bits 0-3 are
greater than nine,
or
if
AC is one, the
accumulator
is incremented by six.
The
four
high-order
bits are then checked.
If
bits
4-7 exceed nine,
or
if
C is one, these bits are
increased by six.
If
an
overflow occurs, C is
set to one.
I
Example: Assume
accumulator
contains 10011011.
DA A ;ACC ADJUSTED TO 00000001
;WITH C
SET
C
AC
7 4 3 0
o
010011011
o 1 1 0
ADD
SIX
TO
BITS 0-7
o
010100001
o 1 1 0
ADD
SIX TO BITS 4-7
1
0 0 0 0 0 0 0 0 1 OVERFLOW TO C
DEC A Decrement Accumulator
10000101111
The contents
of
the
accumulator
are decremented by one.
(A)
__
(A)-1
Mnemonics
copyright
Intel Corporation 1976.
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