Intel MCS48 User Manual page 417

MODEL
220
the IPB transfers a
character
for display to
the IOC,
where
it
is
stored
in
RAM. The
CRT
controller
reads a
line at
a
time
into
its
line
buffer
through an
Intel
8257
DMA
controller
and then feeds
one
character
at
a time
to
the character generator
to
produce
the video signal.
Timing
for
the
CRT
control
is
provided by an
Intel
8253
interval
timer.
The
screen display
is
formatted as 25
rows
of 80 characters.
The
full
set of
ASCII characters
are displayed, including lower-case alphas.
Keyboard
—
The keyboard
interfaces directly to
the
IOC
processor
via
an
8-bit
data bus.
The keyboard contains
an
Intel
UPI-41 Universal Peripheral
Interface,
which
scans
the keyboard,
encodes the characters,
and
buf-
fers
the characters
to
provide
N-key
rollover.
The
key-
board
itself
is
a high
quality typewriter-style
keyboard
containing the
full
ASCII character
set.
An
upper/lower
case switch allows the
system
to
be used
for
document
preparation.
Cursor control
keys
are also provided.
Floppy
Disk Drive
The
floppy disk drive
is
controlled by an
Intel
8271
single
chip,
programmable floppy disk
controller.
It
transfers
data
via
an
Intel
8257
DMA
controller
between
an IOC
RAM
buffer
and the
diskette.
The
8271 handles
reading
and
writing of data,
formatting
diskettes,
and
reading status,
all
upon
appropriate
commands
from the
IOC
microprocessor.
Peripheral Interface
A
UPI-41 Universal Peripheral Interface
on
the
IOC board
performs
similar
functions
to
the UPI-41
on
the
PIO
board
in
the
Model
210.
It
provides interface
for
other
standard
Intellec
peripherals, including a
printer,
high
speed paper tape
reader,
high
speed paper tape punch,
and universal
PROM
programmer.
Communication
between
the
IPB
and IOC
is
maintained over a
separate,
8-bit
bidirectional
data
bus.
Connectors
for
the devices
named
above, as well
as the two
serial
channels, are
mounted
directly
on
the
IOC
itself.
Control
User
control
is
maintained through a
front
panel con-
sisting of
a
power
switch and
indicator,
reset/boot
switch, run/halt
light,
and
eight interrupt
switches
and
indicators,
the front-panel circuit
board
is
attached
directly to
the IPB, allowing the eight interrupt
switches
to
connect
to
the primary 8259, as well
as
to
the
Intellec
Series
II
bus.
MULTIBUS
Capability
All
Intellec
Series
II
models implement
the
industry-
standard
MULTIBUS.
MULTIBUS
enables
several
bus
masters,
such
as
CPU
and
DMA
devices, to
share the
bus and
memory
by operating
at
different priority levels.
Resolution
of
bus exchanges
is
synchronized by a
bus
clock signal derived
independently from processor
clocks.
Read/write transfers
may
take place
at
rates
up
to
5
MHz. The bus
structure
is
suitable
for
use with
any
Intel
microcomputer
family.
Expansion
The Model 220
may
be
expanded
to
64K
of
RAM
and up
to
2.25M
bytes of on-line diskette storage.
SPECIFICATIONS
Host Processor
(IPB)
8080A-2 based,
operating
at
2.600
MHz.
RAM
—
32K,
expandable
to
64K
with
iSBC
032
RAM
boards (system monitor occupies
62K
through 64K)
ROM
—
4K
(2K
in
monitor,
2K
in
boot/diagnostic)
Bus
—
MULTIBUS,
maximum
transfer rate of 5
MHz
Clocks
—
Host
processor, crystal controlled
at 2.6
MHz,
bus
clock, crystal controlled
at
9.8304
MHz
I/O Interfaces
2
Serial I/O
Channels,
RS232C,
at
110-9600 baud
(asyn-
chronous)
or 150-56K
baud
(synchronous).
Baud
rates
and
serial
format
fully
programmable
using
Intel
8251
USARTs.
Serial
Channel
1
additionally provided with 20
mA
current
loop. Parallel I/O interfaces
provided
for
paper tape punch, paper tape
reader,
printer,
and
UPP-103
Universal
PROM
Programmer.
Interrupts
8-level,
maskable, nested
priority interrupt
network
initi-
ated from
front panel or user selected
devices.
Direct
Memory Access (DMA)
Standard capability
on
MULTIBUS;
implemented
for
user selected
DMA
devices through optional
DMA
module
—
maximum
transfer rate of 2
MHz.
Memory Access Time
RAM
—
585 ns
max
PROM
—
450 ns
max
Diskette
Diskette
System
Capacity
—
250K
bytes (formatted)
Diskette
System
Transfer Rate
—
160K
bits/sec
Diskette
System Access Time
Track-to-Track: 10
ms
max
Average
Random
Positioning:
260
ms max
Rotational
Speed: 360
rpm
Average
Rotational Latency:
83
ms max
Recording
Mode:
FM
Physical Characteristics
Width—
17.37
in.
(44.12
cm)
Height
—
15.81
in.
(40.16
cm)
Depth
—
19.13
in.
(48.59
cm)
Weight
-
86
lb (39 kg)
9-3