User Guide

Nokia Customer Care Baseband Description and Troubleshooting

2118 (RH-77)

Figure 3: Measured power-on sequence and timing

Power Up - Power Key

When the power key is pressed, the UEMC enters the power-up sequence. Pressing the

power key causes the PWRONX pin on the UEMC to be grounded. The UEMC PWRONX

signal is not part of the keypad matrix. The power key is only connected to the UEMC.

This means that when pressing the power key an interrupt is generated to the UPP that

starts the MCU. The MCU then reads the UEMC interrupt register and notices that it is a

PWRONX interrupt. The MCU reads the status of the PWRONX signal using the UEMC

control bus (CBUS). If the PWRONX signal stays low for a certain time the MCU accepts

this as a valid power-on state and continues with the SW initialization of the baseband.

If the power key does not indicate a valid power-on situation, the MCU powers off the

baseband.

Power Up - Charger

In order to be able to detect and start charging in cases where the main battery is fully

discharged (empty) and hence UEMC has no supply (NO_SUPPLY or BACKUP mode of

UEMC), charging is controlled by start-up charging circuitry.

Whenever the VBAT level is detected to be below the master reset threshold (V

MSTR-

charging is controlled by START_UP charge circuitry. Connecting a charger forces the