Lines Of Ports - Intel MCS48 User Manual

INTELLEC
PROMPT
48
Documentation
The
PROMPT
48
manual includes chapters
for
the
reader with
little
or
no programming experience.
Topics
treated
range from
number systems
to
microcomputer
hardware
design.
A
novel, unifying
set
of
tutorial
diagrams
—
MICROMAPS
—
simplify
microcomputer
concepts.
PROMPT'S
handy, pocket-sized reference
cardlet
can be
affixed to
the
mainframe.
Programming
pads
aid
in
the organization
and documentation
of pro-
grams.
These features, plus
a
comprehensive
design
library
of
manuals,
articles,
and application notes,
make
the
Intellec
PROMPT
48
ideal for
the
newcomer
to
microcomputing.
SPECIFICATIONS
Timing
Basic Instruction
—
2.5 ms
CycUi
Time
—
t CY
=
2.5
^s
Clock
-6
MHz
±
0.1%
Memory
Bytes
The
8748 contains 64 bytes
of register
memory, no
ex-
ternal
data
memory, and 1024 bytes
of
RAM
program
memory. The
PROMPT
system
provides
256
bytes of ex-
ternal
data
memory, and
1024 bytes
of
RAM
program
memory.
PROMPT RAM
program
memory
can be used
in
place of
the on-chip
EPROM
program memory;
thus
programs
less
than 1024 bytes
may
be designed. For
larger
programs
additional
memory
can be
directly
in-
terfaced
to
the
MCS-48
bus
via
the
PROMPT
panel
I/O
ports
and bus connector.
Memory
Configuration
Memory Maximum On
Chip
In
PROMPT
48
Register
Data
Program
64
3328
4096
64
1024
EPROM
256
1024
RAM
I/O
Ports
All
MCS-48
I/O
ports are accessible
on
the
PROMPT
pane
connector.
Bus
—
A
true bidirectional
8-bit
port
with associated
strobes.
If
the
bidirectional
feature
is
not
needed, bus
can serve as
either
a
statically
latched output port or a
non-latching input
port.
Input
and
output
lines
cannot
be
m
xed.
Ports
1
and 2
—
Data
written to
these
8-bit
ports
is
latched
and remains unchanged
until written.
As
inputs
these lines are not latching.
The
lines of
ports
1
and
2
are called quasibidirectional.
A
special
output
structure
allows each
line of port
1
and
half
of port 2
to
serve as
an
input,
an
output, or both.
Any mix
of input,
output,
and
both
lines
is
allowed.
TO,
Til,
and INT
—
Three
pins that
can
serve as
inputs.
TO
can be designated
as a clock output. Input/output
can
be
expanded
via the
PROMPT
panel connector
with a
special
I/O
expander
(8243) or standard
peripherals.
Reset
and
Interrupts
Reset
—
initializes
the
PROMPT
system and
enters the
monitor.
Monitor
Interrupt
—
exits a user
program
gracefully,
preserving
system
status
and
entering the monitor.
User
Interrupt
—
causes an
interrupt
only
if
the
PROMPT
system
is
running
a user program.
The
processor traps
to
location 3
16 .
The MCS-48
timer/-
event counter
is
not
used by the
PROMPT
system and
is
available to the user. Either timer
flag
or interrupt
will
signal
when
overflow has occurred.
The
timer interrupt
can be used
only
in
the go-no-break
(real
time)
mode.
EPROM
Programming
PROMPT
48 provides a
programming
socket to directly
program
8748s.
Programs
are
loaded
into the
PROMPT
RAM
program
memory
via
keyboard.
EPROM,
teletype-
writer,
or
other
serial interface.
A
fail-safe
interlock
ensures
programming
pulses are applied only
if
the
device
is
properly inserted. Inadvertant
reprogramming
is
prevented by a read-before-write
programming
algo-
rithm.
Each
location
may
be
individually
programmed,
one byte
at
a
time.
Panel
I/O
Ports
and Bus Connectors
All
MCS-48
pins,
except
five,
are accessible
on
the
I/O
ports
and bus connector.
The
five
reserved for
PROMPT
system
control are
EA
external access,
SS
single step,
X1,
X2
crystal inputs,
and
5V.
Due
to internal
buffering
of
the
MCS-48
bus,
access times
will
be
negligibly
degraded by the
PROMPT
system. Since
MCS-48
pro-
cessors
do
not
communicate
internal
address gate
status,
bus data
must
be driven out
if
neither
PSEN
nor
RD
is
asserted.
System Devices
Both user
programs and
the
PROMPT
monitor enjoy
ac-
cess
to
system
devices:
serial I/O,
panel displays,
and
keyboard.
These
are
memory-mapped
to
program
memory
addresses beyond
2K.
Serial I/O
—
The
serial I/O port (data
820
16
,
control 821
16
)
is
defined by software
and jumpers
for
110 baud, 20
mA
current
loop,
but
can
easily
be
jumpered
for
other baud
rates
and RS232C
levels.
Asynchronous
or
synchronous
transmission, data
format, control characters,
and
par-
ity
can be programmed.
Panel Displays
—
Eight display ports (data
810-817
16
)
allow each
of
the panel displays
to
be
written
from user
programs. Data
written
on
a display device
will
time out
after
a fixed
interval.
Displays
must be
refreshed
on
a
polled or interrupt-driven basis.
User programs can
call
software
drivers
which
provide this capability.
9-13