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4Ć49
Troubleshooting the System
If the qualifier
is . . . Then . . .
1 testing occurs at power-up initialization and before each zero
and slope calibration. The ±12V is checked before and after
every sample measurement. A GO pulse is sent to the CMB.
PWRGOOD is polled to determine if the power supplies are
within range. .
2 testing occurs at power-up initialization and before each zero
and slope calibration. A GO pulse is sent to the CMB. A
counter verifies if the CMB generates 256 interrupts on
ADCRDY. Integration time and CMB DAC value is checked.
3 testing occurs at power-up initialization and before each zero
and slope calibration. Ground input to the ADC on the CMB
is selected. A GO pulse is issued sent to the CMB and the
resulting 256 values are averaged. An error is reported if the
average value is outside the range 7F00
H
to 80FF
H
.
4 testing occurs only at power-up initialization. The DAC value
016F
H
is loaded. A dark measurement is initiated, the DAC is
loaded with 05D0
H
, and another dark measurement is taken.
The difference in ADC counts between the two measurements
is to be 32,768 ±200 counts.
5 testing occurs at power-up initialization and before each zero
and slope calibration. Ground is selected as the ADC input. A
GO pulse is issued. The resulting 256 values are collected and
the SD computed. An error is reported if SD is greater than
3.30 ADC counts.
6
testing occurs at power-up initialization and any time a heater
control error is detected. This tests the integral non-linearity
of the DAC. The DAC is alternately set to zero, mid-, and full
scale. The output is read at each level. The value at each level
must be within 100 mV after subtracting the offset of the
GPADC (Refer to qualifier 11.):
S Program 0 value into the DAC and read 0 ±100 mV.
S Program 2047 into the DAC and read 2500 ±100 mV.
S Program 4095 into the DAC and read 5000 ±100 mV.
(Continued)