Intel MCS48 User Manual page 271

8212
Applications
of
the
8212
—
For
Microcomputer Systems
I
Basic
Schematic
Symbol
II
Gated Buffer
III
Bi-Directional
Bus
Driver
IV
Interrupting Input Port
V
Interrupt Instruction Port
VI
Output
Port
VII
8080
A
Status Latch
VIM
8085
A
Address
Latch
1.
Basic
Schematic
Symbols
Two
examples
of
ways
to
draw
the
8212 on system
schematics
—
(1
)
the
top being the
detailed
view
showing
pin
numbers, and
(2)
the
bottom being the symbolic view
showing the
system
input or
output as a
system bus (bus
containing 8
parallel lines).
The
output
to
the data
bus
is
symbolic
in
referencing 8
parallel lines.
BASIC
SCHEMATIC SYMBOLS
INPUT
DEVICE
OUTPUT
DEVICE
SYSTEM
INPUT
II.
Gated
Buffer (3-State)
The
simplest use
of
the
8212
is
that of a gated buffer.
By
tying the
mode
signal
low and
the strobe input high, the
data
latch
is
acting as a straight
through
gate.
The
output
buff ers
are then enabled from
the device selection logic
DS1 and DS2.
When
the device selection
logic
is
false,
the outputs are
3-
state.
When
the device
selection logic
is
true,
the input data
from
the
system
is
directly
transferred to the output.
The
input
data load
is
250 micro amps.
The
output data
can
sink 15
milli
amps. The minimum
high output
is
3.65
volts.
GATED
BUFFER
7-33