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MAINTENANCE
Front Panel Self Test
The self test can also be run by using front panel Program
1. To run the self test from the front panel, press the follow-
ing buttons in sequence:
SHIFT, OTHER, UPRANGE,
ENTER
The unit will then run the test and display
any error
messages as previously
described.
The self test procedure
is as follows:
1. The display indicates SELFTESTING
for one second.
2. ROM and RAM on the mother board are tested. Dur-
ing this test, the display blanks. The ROM test computes
a 16.bit bytewise checksum on each of the three ROMs,
and compares these against the checksums which were
calculated
and stored when the software
was com-
piled. The RAM test checks each byte location by stor-
ing a test pattern and then reading it back to see if it
reads what it wrote.
3. The display lights up with all segments, decimal points,
and annunciators
on.
4. Any A/D boards installed are tested. The A/D test is as
follows:
A. The A/D is programmed to take 20400 16-bit samples
at 100psec interval, with GND input coupling, on the
3OOmV range. The measurement
is performed
and
timed, and the actual time it took is compared to
what it should have taken. If the actual measurement
time is not within
10% of the calculated
time, it
signifies
a timebase error.
B. The A/D memory pointer
is examined
to see if it
wrapped around 7FFF hex. If it did, the jumper on
the A/D board is set for 32K; otherwise
it is set for
64K. This information
is stored for use by the A/D
operating
software.
C. Now that the extent of the A/D RAM is known,
the
RAM is tested using the same algorithm as that used
for the mother board RAM.
D. The standard
deviation
of the measurement
is
calculated.
If the result is more than one millivolt,
it indicates a noisy A/D error.
5. The results of the self tests are examined-if no errors are
detected, the display shows SELETEST PASS for one se-
cond and then the 194 proceeds with whatever it is that
it is supposed to do. Also, the value 01 is stored in the
self test field of the UO string for IEEE-488 output.
6. If any errors are detected, the highest numbered one is
displayed for one second, and its number stored in the
self test field of the UO string.
IEEE-488 Bus Self Test
To perform the self test over the IEEE-488 bus, simply send
the following
command over the bus: JlX. The self test bit
in the Ul status word can then be checked to determine
whether
the test passed or failed. Figure 7-14 shows the
general format of the Ul status word and the values that
flag self test pass or fail conditions.
Note that the nature
of the errcx can be deteremined
by checking the values
of the J bytes, as described in paragraph 4.9.15.
Figure 7-13. Ul Status Word Format
7-26
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