Intel MCS48 User Manual page 31

INTRODUCTION
1.3
Developing
An MCS-48™
Based
Product
Although
the
development
of
a
microcom-
puter
based product
may
differ in detail
from
the
development
cycle
of
a product based
on
TTL
logic or
relays,
the basic
procedures
are
the
same
—
only the tools are
different.
1.3.1
Education
The
first
step
of
course
is
to
become
familiar
with
what
the
microcomputer
is
and what
it
can
do.
The
first
step
in
this
education
is
this
document,
the
MCS-48™
User's
Manual.
The
user's
manual
gives a detailed description of
the
MCS-48
family of
components and
how
they
may
be used
in
various
system
configu-
rations.
Also included
is
a description of the
8048
instruction
set
and examples
of
how
the
instructions
may
be
used.
For a
more
complete
discussion
of the instruction set
and programming
techniques the
MCS-48
Assembly Language Manual
is
also available.
If
time
is
critical in
getting started
in
microcomputers,
individuals
can
attend
one
of
many
Intel
sponsored 5-day
training
courses which
give basic instruction
in
the
MCS-48
as
well as
hands-on
experience
with
MCS-48
development
systems.
These
courses
are a convenient
means
of getting
started with the
MCS-48,
particularly for
those
not
familiar
with microprocessors.
After general
familiarization
is
complete,
either
through
self-instruction or a
training
course, the next step
is
to
gain a
better "feel"
for
what
a
microprocessor can do
in
your
own
applications
by
writing several exercise
programs which
perform
basic functions.
You
may
require
such
things as I/O
routines,
delays, counting
functions,
look-up
tables,
arithmetic functions, and
logical
operations
which can
serve as a
set of building
blocks
for
future applications programs.
Several basic
programming examples
are included
in
the
MCS-48
Assembly Language Manual
while
the
Intel
User's Library
is
a
source
of
more
specific applications
routines.
1.3.2
Function
Definition
After a
thorough
understanding
of the
microprocessor
is
achieved, the functions
to
be implemented can be
defined using a
flowchart
method
to
describe
each
basic
system
function
and
the
sequence
in
which
the
processor executes these
functions.
Once
the
system
is
flowcharted,
critical
time-
related
functions
can
be
identified
and
sample programs
written to
verify
that
performance
requirements can be
met.
1.3.3
Hardware
Configuration
The
next step involves the
definition of the
microcomputer hardware
required
to
imple-
ment
the function.
Input/Output
capability
must be
defined
in
terms
of
number
of inputs,
number
of outputs,
bi-directional
lines,
latching or
non-latching
I/O,
output
drive
capability,
and
input
impedance.
The num-
ber
of
words
of
RAM
storage required
for
intermediate
results
and
data storage
must
then be determined.
The
type
of
system
will
dictate
whether
battery
backup
is
needed
to
maintain data
RAM
during
power
failure.
Probably the
most
difficult
parameter
to
define
initially is
the
amount
of
program
memory
needed
to store the applications
program. Although
previously written exer-
cise
programs
will
make
this
estimate
more
accurate,
a
generous amount
of
"breathing
room"
should be allowed
in
program
memory
until
coding
is
complete and
the exact
requirements
are
known. Many
special
functions
such
as
serial
communications
(TTY)
or
keyboard/display
interfaces
may
be
implemented
in
software (programs);
how-
ever,
in
cases
where
these functions place a
severe load
on
the processor
in
terms
of
time
or
program
memory,
special peripheral
interface
circuits
such
as the 8251, Universal
Synchronous
or
Asychronous
Receiver/
Transmitter
(USART)
or
8279 Keyboard/
Display
interface
may
be
used.
1.3.4
Code
Generation
The
writing of the
final
program code
for
the
application
can
begin
once
the system
function
and hardware have been
defined
and can
be generated
in
parallel
with the
detailed
hardware
design (PC
card
layout,
power
supply,
etc.)
1-13