Advertisement
Model
34SSA
THEORY
OF OPERATION
Section
Vlll
of
US8
high
to latch the
switch
code and
also
sets
the
inter-
rupt
input to the
main
processor.
8-171
.
Upon
recognizing the
interrupt input, the
processor
sets
the interrupt
enable
output
high
to
enable buffers
U59
and
U60
and
reads the switch code. This
code
represents a
vector address to the processor.
The
processor
performs
the
program
routine
contained
at
the address indicated
which
includes transferring the
new
switch data
to the
inguard
controller
and
outputting data
to the front
panel
to
change
the necessary cnunciators.
8-172.
The new
enunciator data
is
output
to the
data
bus
(lines
D0
through
D7) by
the
main
processor
and
applied to
the inputs
of
latches
U6S
through U70.
The new
enunciator
code
is
contained
on
lines
00
through 05.
Lines
06
and
07
are
applied
to the
select
inputs
of decoder
U64
and
arc
used
to
determine
which output of
U64
will
be
set
low.
Outputs
1Y0
through
1Y3
are
enabled
by
the
signal
from
device
select
decoder U41. Outputs
2Y0
and
2Y1
are
enabled
by
8-173.
Display.
Measurement
data
is
transferred
to
the
display
one
number
at
a time.
The
polarity
or numerical
data
is
applied
to the
input
of
latch
US4
and
the
digit
(or
position
in
the display)
and decimal information
is
applied
to
the
input
of
latch
U63.
The
output of
device
select
decoder
U41
is
applied
to the
clock input
of
US4
and
U63
to latch the
information.
The
position
information
is
ap-
device
select
decoder U33.
The
outputs of
U64
are
acti-
vated
by
the
delayed clock
signal
from
U52F
and
applied
to
the clock inputs
of
latches
U6S
through U70.
All
outputs
of
U64
are
high
except
the
one
driving the latch
which
is
to accept the
data.
The
enunciators
are
lit
when
the
output of
the
latch driving
them
is
set
low.
plied
to
the
select
and
data inputs
of
US6
to
determine
the
proper
display driver to
be
activated.
The
outputs
of
U.56
are
applied
to
the display
drivers
(Q1
1
throu^ Q18)
and
are
enabled
by- the
signal
from
U48B
(interrupt
circuitry).
The
display
is
scanned
from
left
to
right
one
number
at a
time.
8-33/8-34
Advertisement
