Radio Power-Up/Power-Down Sequence - Motorola ASTRO XTS 3000 Service Manual

Radio Power-Up/
Power-Down
Sequence
Radio power-up begins when the user closes the radio on/off switch on
the control top, placing 7.5Vdc on the B+_SENSE line. This signal
enables the pass element Q106 through Q105, enabling SW_B+ to the
controller board and the transceiver board. B+_SENSE also enables the
+5Vdc regulator, U709. When +5Vdc has been established, it is sensed
by the supervisory IC, U726, which disables the system reset through
the delay circuit R208 and C214.
When the MCU comes out of reset, it fetches the reset vector in ROM
at $FFFE, $FFFF and begins to execute the code this vector points to. It
configures the SLIC through the parallel bus registers. Among other
things it enables the correct memory map for the MCU. It configures
all the transceiver devices on the SPI bus. The MCU then pulls the
ADSIC out of reset and, after a minimal delay, the DSP also. It then
configures the ADSIC via the SPI bus, configuring, among other
things, the DSP memory map. While this is happening, the DSP is
fetching code from 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 controller 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 Q106 and shutting down the 5Vdc regulator U709. When the
regulator slumps to about 4.7Vdc, supervisory IC U726 activates a
system reset to the SLIC, which in turn resets the MCU.
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