Nokia 3555 Service Manual page 63

RM-257; RM-270; RM-277
BB Troubleshooting and Manual Tuning Guide
1 User presses the power/end key -> PWRONX is low.
2 Vilma activates Vana, VIO, VDRAM (1.8V), sleep oscillator and VR1 -> VCTCXO starts running, Digital ASIC
gets system clock, I/O buffers are powered, FLASH devices are powered. Vilma raises RstX signal to Betty.
3 Betty starts Vcore regulator immediately when RstX rises. Due to soft start this however may take up to
1 ms.
4 RF clock is stable.
5 After 16 ms Vilma releases PURX -> Digital ASICs start their boot sequence. RAP3G can switch SW controlled
regulators on/off, RAP3G controls sleeping by SleepX signal.
6 RAP3G is powered up.
Note: SleepX signal is raised at the beginning of start up procedure and it does not go to zero before
system is really ready to go to sleep. This differs from behaviour in previous generations.
Issue 1
Figure 5 Power up timing
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