Intel MCS48 User Manual page 273

8212
VI.
Output Port (With
Hand-Shaking)
The
821 2
can be used
to
transmit data
from
the data
bus
to
a
system
output.
The output strobe could be
a
hand-
shaking signal
such as "reception
of
data"
from the device
that the
system
is
outputting
to.
It
in
turn,
can interrupt the
system
signifying the
reception of data.
The
s
elec tion of
the port
comes
from the device selection logic.(DS1
•
DS2)
OUTPUT PORT
(WITH
HAND-SHAKING)
SYSTEM
INTERRUPT
OUTPUT STROBE
SYSTEM OUTPUT
SYSTEM RESET
PORT SELECTION
-
(LATCH
CONTROL)
(DS1-DS2)
VII.
8080
A
Status Latch
Here
the
8212
is
used
as the status latch for
an
8080A
microcomputer
system.
The
input
to
the
8212
latch
is
directly
from
the
8080A
data
bus.
Timing shows
that
when
the
SYNC
signal
is
true,
which
is
connected
to
the
DS2
input
and
the
phase
1
signal
is
true,
which
is
a
TTL
level
coming from the clock generator; then, the status data
will
be latched
into
the 8212.
Note:
The
mode
signal
is
tied
high
so
that the
output
on
the
latch
is
active
and enabled
all
the time.
It is
shown
that the
two areas
of
concern
are the
bi-
directional
data
bus
of
the
microprocessor
and
the control
bus.
-
DATA
BUS
T1
T2
01
f\
v
^
BASIC
,
r
[\
CONTROL
SYNC
r
,
v
—
-1
DATA
STATUS
:c
7-35