Charger Detection; Audio; Displays And Keymat - Nokia 6255 Description And Troubleshooting

6255/6255i6256/6256i (RM-19)
Baseband Description and Troubleshooting

Charger Detection

Connecting a charger creates voltage on the VCHAR input of the UEME. Charging starts
when the UEME detects the VCHAR input voltage level above 2 V (VCH
The VCHARDET signal is generated to indicate the presence of the charger for the SW.
The EM SW controls the charger identification/acceptance.
The charger recognition is initiated when the EM SW receives a "charger connected"
interrupt. The algorithm basically consists of the following 3 steps:
1. Check that the charger output (voltage and current) is within safety limits.
2. Identify the charger as a 2-wire or 3-wire charger.
3. Check that the charger is within the charger window (voltage and current).
If the charger is accepted and identified, the appropriate charging algorithm is initiated.

Audio

The audio control and processing is provided by the UEME, which contains the audio
codec, and by the D2800 processor, which contains the MCU and DSP blocks. These
blocks handle and process the audio data signals.
The baseband supports three microphone inputs and two earpiece outputs. The
microphone inputs are MIC1, MIC2, and MIC3:
• MIC1 is used for the mobile terminal's internal microphone
• MIC2 is used for headsets (HDB-4)
• MIC3 is used for the Universal Headset
Every microphone input can have either a differential or single-ended AC connection to
the UEME circuit. The internal microphone (MIC1) and external microphone (MIC2) for
TM
Pop-port accessory detection are both differential. However, the Universal Headset
interface is single-ended. The microphone signals from different sources are connected
to separate inputs at the UEME. Inputs for the microphone signals are differential types.
Also, MICB1 is used for MIC1 and MICB2 is used for MIC2 and MIC3 (Universal Headset).

Displays and Keymat

The mobile terminal utilizes the main display and a secondary display, as well as an
electroluminescent (EL) panel for the keymat lighting.
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Figure 15: Charging circuit
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