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Baseband troubleshooting
Nokia Customer Care
Figure 82 CBUS waveform
CBusCLk is connected to Ch1, CBusDa to CH2 and CBusEnx to Ch3.
If you are able to get the phone to boot up and can reach Phoenix BB self test feature, it is possible to test the
functionality of each component attached to CBus. Use:
• ST_UEM_CBUS_IF_TEST to test the UEME CBus interface
• ST_ZOCUS_CBUS_IF_TEST to test the ZOCUS CBus interface.
If an error is found in testing any of the above components, you should replace or re-solder the failed component.
FBUS interface
FBUS is a two-wire Rx and Tx interface between UPP_WD2 and flash/test interface. The bus goes through UEME,
which adjusts the voltage levels to suit UPP_WD2.
The interface voltage level on the phone flash/test pad pattern is 2.7V and on the UPP_WD2 end it is 1.8V.
The functionality of this interface should not affect the device boot into NORMAL, LOCAL or TEST modes.
Phoenix tests can be performed through the MBUS interface in the case of a failure in the FBUS interface. Flashing
is not possible if there is a problem in the FBUS interface. Fbus signals located in the flashing test pads and the
pad layout is shown in the figure below.
9235618 (Issue 2)
Company Confidential
Page 6–13
Copyright ©2005 Nokia. All Rights Reserved.
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