13.Monitor A3U401 pin 9 (LV_STB) with an oscilloscope or logic probe. This is the strobe for the A4 Log Amplifier/Cal Oscillator assembly.

14.Press [w) and check that pulses occur when toggling between LINEAR and

LOG DB/DIV .

Interface Strobe Select

See function block K of A3 Interface Assembly Schematic Diagram (sheet 3 of 6).

Interface strobe select generates the various strobes used by circuits on the A3 Interface Assembly. Tables 7-10 and 7-11 are the truth tables for demultiplexers A3U410 and A3U500.

Table 7-10. Demultiplexer A3U410 Truth Table

Selected Outmt he

IA1

IA2

IA3

Pin 15, LSCAN_KBD

L

L

L

Pin 14, not used

H

L

L

Pin

13, LDACl

L

H

L

Pin 12, LDAC2

H

H

L

Pin 11, LDACS

L

L

H

Pin

10,

not used

H

L

H

Pin

9,

not used

L

H

H

Pin 7, LADC-REGl

H

H

H

Table 7-11. Demultiplexer A3U500 Truth Table

Selected Output Line

IA0

IA1

IA2

Pin 15, LSENSE-KBD

L

L

L

Pin 14, LINT_PRIOR

H

L

L

Pin 13, LADC_DATA1

L

H

L

Pin 12, LDAC_DATA0

H

H

L

Pin 11, HCNTR_LDO

L

L

H

Pin 10, HCNTR-LDl

H

L

H

Pin 9, LRPG_RD

L

H

H

Pin 7, LADC_REGO

H

H

H

7-28 ADC/lnterface Section