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Model
5315A/B
Service
8-6
8-31.
Overall Block
Theory
6-32. The
5315A/
B
Universal
Co
unter
is
comp rised
of
th
e
follow
ing functional blocks:
a.
Input
Channels
(A&B)
b.
M
ul
tiple-Register-Counter (MRC)
c.
Microcomputer
d.
Display/Expone
nt Decoder
Drivers
e.
Display
f.
Function
Switches
g.
Power Supp ly
6-33. There are
two
basically
identical
input c
hann
els,
whi
ch cond
ition
and
shape
the
input
signa ls. Front
panel
controls
allow
individ
ua
l
select
ion
of
AC/
DC
co
upling,
ATTEN, SLO
PE,
and
SEP/
COM
A
configuration
.
Input
amp lifiers
and co mparators
buffer
and square the sig nals,
and
set the desired trigger level
(or
sehsitivity).
The
signa ls are
then
level-shifted
and
inpu
t to
the
M RC as Cha
nn el
A
and
Chann
el
B.
The MRC receives inputs
from Channels
A
and
Band
the
reference
oscillator, and then,
via com mands from the
j.l.C,
performs
the data
collect
ion
for
th
e fu nctio
n
mode
specified
by
front panel contro
ls.
6-34.
To
make
a measu rement,
the
microcomputer
routinely scans
and
stores the
Function
Switches,
and then
config ures the MRC, via
the Address/Command
bus,
to the
desired measure-
ment mode (i.e.,
frequ
ency, period, time interva l, tota
li
ze,
etc. ).
It
the
n
"arms" the
M RC, which
allows the
meas urement
to
begin.
The
input
signal
to the
MRC starts the measurement,
and
when
the
Gate Time O
ne-Shot
ti mes o
ut,
the MRC signals
the microcomputer
(via
IRQ
)
that the
measureme nt is
complete. The microcomputer will
the
n
read the measu rement data
from th
e
MRC,
manipulate it
if
necessary
and then
direct
it to
the
Display
Driver. The
Display
Driver
receives,
decodes.
and then displays
the
data.
The
exponent,
exponent
sig
n,
a nd decima
l
po
int
are
si multa neously computed
within
the
microcomputer and
d isplayed, along
with
theappropri-
ate annu
nci
ato
r.
Depending on the
functio
n
mode,
the
microcomputer
will
the
n
typica
ll
y
reconfigure
the MRC
and repeat th
e
cycle
until
the
Funct ion Switches
are
c hanged.
6-35. The power
supply provides
three regulated
voltages; +5V dc,
+3V
dc, and -5.2V dc,
and an
unregulated ""+9V
dc
for
use
with options.
6-36. Assembly Circuit Theory
6-37.
The follow
ing
paragraphs reference
the
schematic
diagrams
in
Figures
8-7
th rough
8-9
and
descri be the
detailed circuit theory.
8-38.
A1 Motherboard
6-39. The
motherboard
assem bly
contains
the
microcomputer,
multiple register cou nte
r,
function
sw
itches,
internal
oscillator and
power
supp ly. The
microcompu te
r runs
at an internal
clock rate of ""2.5
M Hz, as set
by
Ll.
It
continu
ally cycles throug
h
programmed routines, wh ich
are stored
in
ROM
with
in
the
IC The
block
of
fundio
n sw itches are ro
uti
nely po
lled,
via
the
Switch
Status
bus,
and
the
status image
is
stored
in
intern
al
RAM.
Any
change in
the
image
is
detected,
and
verified. A new funct io
n
switch
setting
must remai
n
stable fo
r
32 scans
to be
accepted.
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