Motorola Commercial Series Service Information page 30

3-14
IC Designator
U451
ASFIC_CMP
Pin Pin Function
14 GCB1 general purpose output
15 GCB0 general purpose output
16 Squelch channel activity output
17 Squelch detect digital output
18 PL/low speed data I/O
19 High speed data I/O
20 Chip select
21 Serial clock input
22 Serial data input
23 Ground for clock synthesizer
24 Loop filter cap for clock syn
25 PLCAP2 for LS integrator
26 Not used
27 Vdd for clock synthesizer
28 Clock synthesizer output
29 1200 Hz ref for MDC decode
30 GNDDO
31 Ground for digital circuits
32 Vdd for analog switches
33 Vdd for digital circuits
34 16.8 MHz master clock input
35 GCB3 general purpose output
36 TX audio return from option
37 GCB4 general purpose output
38 GCB5 general purpose output
39 RX audio send to option
40 Modulation output
41 RX audio out to power amp
42 Flat TX audio return from option
43 RX audio return to option
44 Flat TX audio send to option
45 Vdd for audio path I/O filters
46 Mic audio input
47 Ground for audio path I/O filters
48 Ext mic audio input (not used)
TROUBLESHOOTING TABLES
DC Voltage Comments (Condition)
0
3.00 BW select (25 kHz mode)
0 To U401-84
0 To U401-83
1.50
3.00
3.23 From U401-2
0
3.23
GND
0.74
1.17
0
3.00
1.70
3.00
GND
GND
4.96
3.00
1.54
3.00 Internal MIC enable
0
0
0
1.48
1.50 To U201-10
1.51
0.20
1.50
1.50
3.00
1.50
GND
0