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Troubleshooting

2-81

Bit patterns

Test 406.3 — Read sample and hold for test 406.6 comparison

Type

Circuit Exercise

Fault message None

Description This test is the same as test 406.2 except that the value is stored for use in comparison calculation

in test phase 406.6.

Drawing reference Analog Board; 2002-100

Bit patterns

Test 406.4 — Read DAC V for sample and hold test 406.6

Type Circuit Exercise

Fault message None

Description DAC U433 and op amp pair U430 are set up to generate -0.01 VDC at PRECOMP+ and tied to

ACF through R491 and U412. ACF is tied to pin 7 of multiplexer U414. The output of the mul-

tiplexer is tied to the A/D through buffer U403, ACV/A input to U222, and the A/D buffer in X1

gain conﬁguration. The value of the DAC voltage is measured and stored. This value will also

be applied to the circuit in tests 406.5 and 406.6. In this manner, the applied value to the circuit

Bit pattern* Register

—U400—

01011101

—U811—

00001101

—U224—

00010111

—U432—

01100100

—U810—

00000011

—U206—

01110000

—U203—

10001110

—U411—

11111011

—U809—

11100111

—U207—

11001111

—U221—

11101001

—U406—

01001101

AD_STB

MUX_STB

R1_STB

R2_STB

*Bits associated with register IC terminals as follows:

QQQQQQQQ

87654321 87654321 87654321 87654321

IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.