Power Up And Reset - Nokia RH-27 Series Technical Documentation Manual

RH-27
Troubleshooting - Baseband

Power Up and Reset

Power up and reset is controlled by the UEM ASIC. RH-27 baseband can be powered up
in the following ways:
1 By the Power button, which means grounding the PWRONX pin of the UEM
2 By connecting the charger to the charger input
3 By the RTC Alarm, when the RTC logic has been programmed to give an alarm
After receiving one of the above signals, the UEM counts a 20ms delay and then enters in
reset mode. The watchdog starts up, and if the battery voltage is greater than Vcoff+, a
200ms delay is started to allow references, etc. to settle. After this delay elapses, the
VFLASH1 regulator is enabled. Then, 500us later VR3, VANA, VIO, and VCORE are enabled.
Finally, the PURX (Power Up Reset) line is held low for 20 ms. This reset, PURX, is fed to
the baseband ASIC UPP; resets are generated for the MCU and the DSP. During this reset
phase, the UEM forces the VCTCXO regulator on — regardless of the status of the sleep
control input signal — to the UEM. The FLSRSTx from the ASIC is used to reset the flash
during power up and to put the flash in power down during sleep. All baseband regula-
tors are switched on when the UEM powers on. The UEM internal watchdogs are running
during the UEM reset state, with the longest watchdog time selected. If the watchdog
expires, the UEM returns to power-off state. The UEM watchdogs are internally acknowl-
edged at the rising edge of the PURX signal in order to always give the same watchdog
response time to the MCU.
The following diagram represents UEM start-up sequence from reset to power-on mode.
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©2003 Nokia Corporation
CCS Technical Documentation
Confidential Issue 1 11/2003