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Model
8904A
Service
A2 DIGITAL ASSEMBLY
General
The
A2
Digital Assembly creates the output waveforms as a series of digital codes (via its DWSIC) and
performs the overall control and functioning of the instrument (via its microprocessor). Specific tasks
include
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control the instrument’s general operation
create the digital waveforms
distribute waveform
data
to
the proper output
control the programmable analog circuits (attenuators, filters, etc.)
retain instrument settings in
RAM
backup
RAM
at power down
process keyboard, HP-IB, digital port, and overvoltage interrupts
scan the keyboard when a key press
is
detected
interface with
HP-IB
generate the reference clocks
switch between internal and external references
control the beeper
generate and time the display backlight
control the front-panel displays and annunciators
output waveform
data
to the digital port
Because some circuits on the assembly are proprietary and because the assembly is available
as
an exchange assembly, a schematic diagram with detailed theory and troubleshooting has not
been provided. Troubleshooting procedures to isolate a fault
to
the assembly can be found in the
troubleshooting section of this manual.
Principles of Operation
(A2) 8-23