Motorola ASTRO Digital Spectra, Detailed Service Manual, Page: 9 / 442

Table of Contents vii
6881076C25-E September 5, 2008
3.1.2.5 Loop Filter ................................................................................................................3-5
3.1.2.6 Auxiliary Control Bits ................................................................................................3-5
3.1.2.7 Second VCO ............................................................................................................3-6
3.1.2.8 Power Distribution ....................................................................................................3-6
3.1.3 Receiver Back-End............................................................................................................3-6
3.1.3.1 First IF ......................................................................................................................3-6
3.1.3.2 ABACUS II IC ...........................................................................................................3-7
3.2 Command Board ............................................................................................................................3-8
3.2.1
Microcontroller and Support ICs........................................................................................3-8
3.2.2 Serial Input/Output IC........................................................................................................3-8
3.2.3 Power-Up/-Down Sequence..............................................................................................3-9
3.2.4 Regulators .......................................................................................................................3-10
3.2.5 Reset Circuits ..................................................................................................................3-10
3.2.6 Serial Communications on the External Bus ...................................................................3-11
3.2.7 Synchronous Serial Bus (MOSI) .....................................................................................3-12
3.2.8 Received Audio ...............................................................................................................3-12
3.2.9 Microphone Audio ...........................................................................................................3-12
3.2.10 Transmit Deviation ..........................................................................................................3-13
3.2.11 RS-232 Line Driver..........................................................................................................3-13
3.2.12 Flash Programming .........................................................................................................3-13
3.2.13 Encryption Voltages ........................................................................................................3-13
3.2.14 Regulator and Power-Control IC .....................................................................................3-14
3.3 ASTRO Spectra VOCON Board...................................................................................................3-15
3.3.1
General............................................................................................................................3-15
3.3.2 Controller Section............................................................................................................3-15
3.3.3 Vocoder Section ..............................................................................................................3-17
3.3.4 RX Signal Path ................................................................................................................3-18
3.3.5 TX Signal Path ................................................................................................................3-21
3.3.6 Controller Bootstrap and Asynchronous Buses...............................................................3-22
3.3.7 Vocoder Bootstrap...........................................................................................................3-24
3.3.8 Serial Peripheral Interface (SPI) Bus ..............................................................................3-24
3.3.9 Controller Memory Map...................................................................................................3-24
3.3.10 Vocoder Memory Map .....................................................................................................3-26
3.3.11 MCU System Clock .........................................................................................................3-28
3.3.12 DSP System Clock ..........................................................................................................3-28
3.3.13 Radio Power-Up/Power-Down Sequence .......................................................................3-28
3.3.14 VOCON Board Signals....................................................................................................3-29
3.4 ASTRO Spectra Plus VOCON Board...........................................................................................3-38
3.4.1
General............................................................................................................................3-38
3.4.2 ASTRO Spectra Plus Controller Section .........................................................................3-38
3.4.3 ASTRO Spectra Plus Vocoder Section ...........................................................................3-39
3.4.4 ASTRO Spectra Plus RX Signal Path .............................................................................3-41
3.4.5 ASTRO Spectra Plus TX Signal Path..............................................................................3-42
3.4.6 ASTRO Spectra Plus Controller Bootstrap and Asynchronous Busses ..........................3-43
3.4.7 ASTRO Spectra Plus Serial Peripheral Interface Bus.....................................................3-44
3.4.8 ASTRO Spectra Plus MCU and DSP System Clocks .....................................................3-44
3.4.9 ASTRO Spectra Plus Voltage Regulators .......................................................................3-45
3.4.10 ASTRO Spectra Plus Radio Power-Up/Power-Down Sequence ....................................3-46
3.5 Voltage Control Oscillator.............................................................................................................3-47
3.5.1
VHF Band........................................................................................................................3-47
3.5.1.1 General...................................................................................................................3-47
3.5.1.2 DC Voltage Supplies ..............................................................................................3-47
3.5.1.3 VCO........................................................................................................................3-47
3.5.1.4 Synthesizer Feedback............................................................................................3-48