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INSTRUCTION SET
4.0 INTRODUCTION
The.
MCS-48
instruction
set is extensive
for
a
machine
of
its size and has been
tailored
to
be
straightforward
and very
efficient
in
its use
of
program
memory. All
instructions
are
either
one
or
two
bytes in length and
over
70% are
only
one
byte
long. Also, all
instructions
execute in
either
one
or
two
cycles
(2.5J.Lsec
or
5.0J.Lsec
when using a 6
MHz
XTAL) and over 50%
of
all
instructions
execute
in a
single
cycle.
Double
cycle
instructions
include
all
immediate
instruc-
tions, and all
I/O
instructions.
The
MCS-48
microcomputers
have been
designed
to
efficiently
handle
arithmetic
operations
in both
binary
and
BCD
as
well
as
to
efficiently
handle
the
single
bit
operations
required in
control
applications.
Special
instructions
have also been
in-
cluded
to
simplify
loop
counters, table
lookup
routines, and
N-way
branch
rou-
tines.
Data Transfers
As can be seen in the accompanying
diagram, the 8-bit
accumulator
is
the central
i-----------l
I
PROGRAM
DATA
I
MEMORY MEMORY
I (!tdata) MOV I
I
ADD I
MOV
MOVP
I MOVP3 I
EXPANDER
,W_---=:..:,:,::-=--J.....J
I/O PORTS
4-7
ANL
ORL
EXTERNAL
MEMORY
AND
PERIPHERALS
8048
8049
8748
I
8035*
*NO
PROGRAM
8039*
I
MEMORY
~
________
---.J
DATA TRANSFER
INSTRUCTIONS
4-1