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INSTRUCTION SET
XCH A,R
r
Exchange Accumulator-Register Contents
1001011rrri
The
contents
of
the
accumulator
and the
contents
of
working
register 'r' are
exchanged.
(A)~
(Rr)
r=0-7
Example: Move PSW
contents
to
Reg 7
without
losing
accumulator
contents.
XCHAR7: XCH A,R7
;EXCHANGE
CONTENTS
OF REG 7
;AND
ACC
MOV
A,
PSW
XCH A,R7
;MOVE
PSW
CONTENTS
TO
ACC
;EXCHANGE
CONTENTS
OF REG 7
;AND
ACC
AGAIN
XCH A,@R
r
Exchange Accumulator and Data Memory Contents
100101000ri
The
contents
of
the
accumulator
and the
contents
of
the
resident data
memory
location
addressed by bits
0-5*of
register 'r' are
exchanged.
Register 'r'
contents
are
unaffected.
(A)~
((Rr))
r=0-1
Example:
Decrement
contents
of
location
52.
DEC52:
MOV
RO,#52
;MOVE
'52' DEC
TO
ADDRESS
;REG 0
XCH A,@RO
;EXCHANGE
CONTENTS
OF
ACC
;AND
LOCATION
52
DEC A
;DECREMENT
ACC
CONTENTS
XCH A,@RO
;EXCHANGE
CONTENTS
OF
ACC
;AND
LOCATION
52
AGAIN
XCHD
A,@R
r
Exchange Accumulator
and
Data Memory 4-Bit Data
100111
000r
l
This
instruction
exchanges
bits 0-3
of
the
accumulator
with
bits 0-3
of
the
data
memory
location
addressed
by
bits 0-5*of register 'r'. Bits 4-7
of
the
accumulator,
bits 4-7
of
the
data
memory
location,
and the
contents
of
register 'r'
-are
unaffected.
(A
O
-
3
)
~
((RrO-3))
r=0-1
Mnemonics
copyright
Intel
Corporation
1976.
4-35
'0-6
for
8039/8049