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things, the DSP memory map. While this is happening, the DSP is
fetching code from the ROM U404 into internal RAM and beginning
to execute it. It then waits for a message from the MCU that the ADSIC
has been configured, before going on.
During this process, the MCU does power diagnostics. These
diagnostics include verifying the MCU system RAM and verifying the
data stored in the internal EEPROM, external EEPROM, and FLASH
ROMs. The MCU queries the DSP for proper status and the results of
DSP self tests. The DSP self tests include testing the system RAM,
verifying the program code in ROM U404, and returning the ADSIC
configuration register checksum. Any failures cause the appropriate
error codes to be sent to the display. If everything is OK, the
appropriate radio state is configured and the unit waits for user input.
On power-down, the user opens the radio on/off switch removing the
B+_SENSE signal from the VOCON board. This does not immediately
remove power as the MCU holds this line active through B+_CNTL.
The MCU then saves pertinent radio status data to the external
EEPROM. Once this is done, B+_CNTL is released shutting off SW_B+
at Q207 and shutting down the 5Vdc regulator U409. When the
regulator slumps to about 4.6Vdc, the supervisory IC U407 activates a
system reset to the SLIC which in turn resets the MCU.
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