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Schottky Bipolar
8228
SYSTEM CONTROLLER AND BUS DRIVER
FOR
8080A
CPU
• Sing.le Chip System Control for
MCS:SO
Systems
• Built-in Bi-Directional Bus Driver
for Data Bus Isolation
• Allows the use
of
Multiple Byte
Instructions (e.g. CAL:L)
for
Interrupt
Acknowledge
• User Selected Single
Leve,1
Interrupt
Vector (RST 7)
• 28 Pin Dual In-Line Package
• Reduces System Package Count
The 8228
is
a single chip system
controller
and bus driver
for
MCS-80.
It
generates all signals required
to
directly interface MCS-80
family
RAM, ROM, and
I/O
components.
A bi-directional bus driver
is
included
to
provide high system
TTL
fan-out.
It
also provides isolation
of
the
8080 data bus
from
memory and
I/O.
This allows
for
the optimization
of
control
signals, enabling the
sys-
tems deisgner
to
use
slower memory and I/O. The isolation
of
the bus driver also provides
for
enhanced
system noise
immunity.
A
user
selected single level
interrupt
vector (RST 7)
is
provided
to
simplify
real
time,
interrupt
driven, small
system requirements. The
8228
also generates the correct control signals
to
allow
the
use
of
multiple
byte
instructions (e.g.,
CALL)
in response
to
an
INTERRUPT
ACKNOWLEDGE
by
the
8080A.
This feature
permits large,
interrupt
driven systems
to
have
an
unlimited number
of
interrupt
levels.
The 8228
is
designed
to
support a wide variety
of
system
bus
structures and also reduce system package
count
for
cost effective, reliable, design
of
the MCS-80 systems.
STSTB
~----------
DBIN
-.0--------------1
WR
-.0-------------011
HLDA
~-------------I
SYSTEM
OAT
A BUS
DRIVER
CONTROL
8228 BLOCK
DIAGRAM
BI·DIRECTIONAL
BUS
DRIVER
PIN CONFIGURATION
STSTB
Vee
HLDA
I/OW
CPU
MEMW
DATA
WR
BUS
OBIN
IIOR
OB4
MEMR
04
INTA
OB7
BUSEN
07
06
OB3
OB6
03
05
DB2
DBS
02
01
DB~
OB1
GND
0'
PIN NAMES
07·00
DATA
BUS (8080 SIDE)
OB7·DBO
DATA
BUS (SYSTEM SIDE)
IIOR
1/0
READ
I!OW
1/0
WRITE
MEMR
MEMORY READ
MEMW
MEMORY
WR
ITE
DBIN
DBIN
(FROM 8080)
INTA
INTERRUPT ACKNOWLEDGE
HLOA
HLDA
(FROM 8080)
WR
WR
(FROM 8080)
BUSEN
BUS
ENABLE INPUT
STSTB
STATUS STROBE (FROM 8224)
Vee
+5V
GND
aVOLTS
5-7