
IMS
INTERNATIONAL
MODEL
740
I/O
PROCESSORBOARD
*
A
GENERAL
DESCRIPTION
The
Model
740I/O
PROCESSOR
isa
singleboardcomputer
with
a
Z-80A
processor,
64K
bytes
of
Dynamic
RAM
with
Parity,
2K
bytes
of
IPL
PROM,
Two
programmable
Synchronous/Asynchronous
communication
channelswith
MODEM
control,
Ten
programmable
parallel
I/O
linescompatible
with
Bell
801
AutomaticCalling
Unit,
Four
intervaltimers
( two
used
for
baud
rates),
Z-80
internally-prioritized
vectored
interruptstructure,
and
Parallelinterface
tothe
S-100
BUS
Host
processor.
The
Z-80A
SIO
interfaces
the
Z-80A
CPUtoTwo
asynchronous
or
synchronousSerial
DataChannels.
TheSIO
converts
input
serialdata
from
the
RS-232Cport
to
parallel
data
tobe
acted
upon
bythe
system.Outputdata
is
converted
from
parallel
to
serial
data
tobe
placed
onthe
RS-232C
port.
The
8255A
Programmable
PeripheralInterfacecircuitinterfaces
the
S-100
BUStothe
slave
Z-80
A
CPU
bus.
The
MODEL
740I/O
Processorconsists
ofa
singleprintedcircuitboard
that
occupies
one
slot
inthe
Series
5000
or
8000
ComputerSystems.Eachserial
RS-232C
port
is
brought
outtoa 3M
26-pin
header.
The
RS-232C
ports
are
designed
as
DataTerminal
Equipment
(DTE)
to
connectdirectly
toa
MODEM.
To
connect
a
terminaldirectly
to
the
RS-232C
port(DTE
to
DTE)
the
RS-232Ccablewires
must
be
interchanged
for
properoperation
of
terminal.
S-100
BUS
TOI/O
PROCESSORINTERFACE
8255A
Mode
2
S-100
BUSto
Slave
Z-80A
CPU
Interface
Due
tothe
drasticreduction
of
hardware
costs,
systemdesigns
which
utilizemultiple
CPU
modules
are
becoming
more
common.
A
Model
451
Z-80A
CPUis
configured
as
the
masterS-100
CPUand
used
to
control
multiple
Z-80A
slave
modules
which
actas
intelligent
I/O
controllers.
When
multiple
CPUs
are
utilized,
a
method
of
processor
intercommunication
must
be
supported.
TheIMS740
Z-80A
module
is
implemented
asa
master/slaveinterfacethrough
theuseofthe
8255A
Mode
2
bidirectionalbus.
The
S-100
BUS
interface
is
supported
byan
8255A
which
is
configued
in
Mode
2.The
8255A
is
selected
through
theuseofa
standardS-100
I/O
Addressdecode
select
scheme
andthe
S-100vectorinterruptstructure.
The
Z-80Aslavelogic
is
implemented
to
allow
the
slave
Z-80A
CPUto
generate
the
ACK-
and
STB-signals
required
to
READ
from
and
WRITE
tothe
8255A
bidirectionalbus.
IMS
INTERNATIONAL
D00740
REV1.0
October
20,
1981
Page
1