Service manual

Table of Contents v
68P81076C25-C July 1, 2002
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
3.5.1.5 RX Buffer Circuitry ................................................................................................. 3-48
3.5.1.6 Frequency Divider and TX Buffer Circuitry ............................................................ 3-48
3.5.2 UHF Band ....................................................................................................................... 3-48
3.5.2.1 General ..................................................................................................................3-48
3.5.2.2 Super Filter 8.6 V................................................................................................... 3-49
3.5.2.3 VCO ....................................................................................................................... 3-49
3.5.2.4 Receive Mode (AUX2* Low) .................................................................................. 3-49
3.5.2.5 Transmit Mode (AUX2* High) ................................................................................ 3-49
3.5.2.6 Bandshift Circuit..................................................................................................... 3-49
3.5.2.7 Output Buffer ......................................................................................................... 3-49
3.5.2.8 First Buffer .............................................................................................................3-49