Digital
Section
Figure
4-6
shows
the
Digital
Section
block
diagram.
Figure
4-6.
Digital
Section
Block
Diagram
The
digital
section
consists
of
the
A2
CPU
Board
Assembly
and
other
peripheral
assemblies
such
as
the
keyboard
and
LCD
.
The
section
communicates
with
the
A1
Main
Board
Assembly
in
order
to
control
the
latches
,
switches
,
and
other
components
on
the
A1
Assembly
and
receive
the
measurement
data.
F
or
the
same
purpose
,
the
A2
Assembly
also
communicates
with
the
A3
Ammeter
Assembly
via
the
A1
Assembly
and
four
optical
bers
.
The
GPIB
interface
on
the
A2
Assembly
allows
the
4339B
communicate
with
a
controller
.
The
handler
interface
on
the
A1
Assembly
allows
the
4339B
communicate
with
an
external
handler
.
Note
Because
of
required
high
dc
isolation
between
the
A3
Assembly
and
other
assemblies
,
the
A3
Assembly
communicates
with
other
assemblies
via
optical
bers
.
The
A2
CPU
Board
Assembly
includes
a
processor
,
ROM,
EEPROM,
jumpers
,
switches
,
and
LEDs
.
ROM
(A2U11)
stores
the
rmware
which
controls
all
the
4339B
operation
and
functions
.
The
ROM
is
mounted
in
a
socket
for
easy
replacement.
EEPROM
(A2U1)
stores
the
unit
unique
data,
such
as
the
adjustment
data
and
the
operator
unique
data,
such
as
the
operator
saved
measurement
setup
condition.
The
EEPROM
will
4-8
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