The baseband is powered up by:
1. Pressing the power key, that generates a PWRONX interrupt signal from the power key to the CCONT, which starts the power up procedure.
2. Connecting a charger to the phone. The CCONT recognizes the charger from the VCHAR voltage and starts the power up procedure.
3. A RTC interrupt. If the real time clock is set to alarm and the phone is switched off, the RTC generates an interrupt signal, when the alarm is gone off. The RTC interrupt signal is connected to the PWRONX line to give a power on signal to the CCONT just like the power key.
4. A battery interrupt. Intelligent battery packs have a possibility to power up the phone. When the battery gives a short (10ms) voltage pulse through the BTEMP pin, the CCONT wakes up and starts the power on procedure.
Power up with a charger
When the charger is connected CCONT will switch on the CCONT digital voltage as soon as the battery voltage exceeds 3.0V. The reset for
CCONT's digital parts is released when the operating voltage is stabilized ( 50 us from switching on the voltages). Operating voltage for VCXO is also switched on. The counter in CCONT digital section will keep MAD in reset for 62 ms (PURX) to make sure that the clock provided by VCXO is stable. After this delay MAD reset is relased, and VCXO -control (SLEEPX) is given to MAD. The next diagram explains the power on procedure with charger ( the picture assumes empty battery, but the situation would be the same with full battery):
When the phone is powered up with an empty battery pack using the standard charger, the charger may not supply enough current for standard powerup procedure and the powerup must be delayed.
Power Up With The Power Switch (PWRONX)
When the power on switch is pressed the PWRONX signal will go low. CCONT will switch on the CCONT digital section and VCXO as was the case with the charger driven power up. If PWRONX is low when the 64 ms delay expires, PURX is released and SLEEPX control goes to MAD. If PWRONX is not low when 64 ms expires, PURX will not be released, and CCONT will go to power off ( digital section will send power off signal to analog parts)
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