Table of Contents
Advertisement
3-1.
INTRODUCTION
3-2.
This
section
of
the
manual
describes the
theory of
operation
for
the
8502A
mainframe,
which
includes the
modules
necessary
for
DC
Volts
and
DC
Ratio measure-
ments. Block
Diagram
descriptions
give
an overview of
the
operation
of
the
modules and an
explanation of
the
bus
structure. Circuit
Analyses
give a
more
detailed description
of
the
circuitry.
Optional
modules
are described
in
Sect.
6.
3-3.
BLOCK DIAGRAM
DESCRIPTION
3-4.
Bus
Structure
3-5.
The
8502A
is
constructed
with
a
bus
archi-
tecture
similar
to a
computer.
Figure
3-1
is
an
overall
block
diagram of
the instrument
with optional
modules drawn
in
dashed
lines.
Figure 3-2
is
a
block diagram
illustrating signal
flow.
A
microprocessor-based
controller
module
controls
information flow
on
the three buses.
The
controller
sets
up
each of the analog
modules
for a
measurement by
address-
ing
the
modules
as
memory
locations.
An
unguarded
digi-
tal
interbus
is
used
to
connect
the
controller to the front
panel
and
to
digital
option
modules
such
as
the calibration
memory
and
a
remote I/O
(input/output)
interface.
3-6.
The unguarded
digital
bus
consists
of the
followini
lines:
1
.
Address/Control
(IC)
lines
—7.
2.
Bidirectional
data (ID)
lines
—8.
3..
Real time
(RT)
lines
—7.
4.
Handshake
lines
(INT—
interrupt,
ACK—
acknow-
ledge,
INA—
interrupt
acknowledge).
5
.
Power
Supply
lines
3
-^
Advertisement
Table of Contents
