Power Up - Power Key; Power Up - Charger Connection - Nokia 6255 Description And Troubleshooting

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Power Up - Power Key

When the power key is pressed, the UEME enters the power-up sequence. Pressing the
power key grounds the PWRONX pin on the UEME. The UEME PWRONX signal is not part
of the keypad matrix. The power key is only connected to the UEME. When the power key
is pressed, an interrupt is generated to the D2800 processor that starts the MCU. The
MCU then reads the UEME interrupt register through the UEME control bus (CBUS) and
notices that it is a PWRONX interrupt. 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 Connection

In order to be able to detect and start charging in cases where the main battery is fully
discharged (empty), charging is controlled by start-up charging circuitry.
The VBAT voltage level is monitored by the Charge Control Block (CHACON) inside the
UEME. When the VBAT level is detected to be below the master reset threshold (V
charging starts. Connecting a charger forces the Charging Voltage (VCHAR) input to rise
above the charger detection threshold (VCH
Issue 2 05/2005
Figure 3: Measured power-on sequence and timing
©2005 Nokia Corporation
6255/6255i6256/6256i (RM-19)
Baseband Description and Troubleshooting
). This causes the UEME to generate
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