Service
TROUBLESHOOTING---SERVICE SHEET
BD1
Model
8903B
KEYBOARDOR
INTERRUF'T
I
CHANGE
SOFTWARE
I
STATE
I
STATE
I
SOURCE
RELATED
HARDWARE SETUP
NO
OSCILLATOR TUNE
m
LEVEL AC INPUT
I
NOTCH TUNE
LEVEL OUTPUT
I
MEASURE FAEOUENCY
PPULfTE DATA
I
OUTPUT
TO
DISPLAYS,
AXIS OUTPUTS
wiB
AND
x
ANDY
SWEEP
I
1.
2.
3.
4.
5.
6.
7.
8.
NOTES
The SOURCE RELATED KEY SCAN block
monitors
the
FREQ, FREQ INCR, AMPTD,
AMPTD INCR,
t
(step up), and
J.
(step down)
keys.
On errors, the instrument exits the current
block, jumps
to
the error return point, and sets
the GUARB (guarantee bit), RESTB (reset bit),
and FIRSTB (first bit).
If RESTB is set, the OSCILLATOR CON-
TROL block will
not
execute and RESTB will
be cleared.
Certain blocks may
or
may not execute during
different measurement modes depending upon
relevancy bits and other conditions.
The OSCOFFB (oscillator
off
bit) is set
on
alternate Signal-to-Noise (S/N) measurement
cycles.
The GUARB indicates
a
valid measurement is
guaranteed. It
is
set by most interrupts, errors,
trigger mode, and under some conditions in the
OVERHEAD
1
block (e.g., it is always set in
Signal-to-Noise measurement mode). It is also
cleared by some conditions in OVERHEAD
1
block.
The FIRSTB indicates the first cycle after an
interrupt
or
error. It is cleared in the OVER-
HEAD
2
block.
MEASlB is set if the instrument is in the
Signal-to-Noise measurement mode and
it
is
the first pass after an interrupt. It takes two
passes to measure Signal-to-Noise. Therefore,
the instrument must restart without
a
display
output and clear MEASlB at the end
of
the
first pass.
Figure
8A-1.
Supervisor Flowchart
8A-6
rev.2OJUN87
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