Nokia NEM-4 Series Troubleshooting Instructions page 135

CCS Technical Documentation
ST_UEM_CBUS_IF_TEST to test UEM Cbus interface
ST_LPRF_IF_TEST to test Bluetooth Cbus interface
If an error is found testing any of the above components you should replace the failing
component.
FBUS
FBUS is a two wire RX and TX interface between UPP and flash/test interface. The bus
goes through UEM which adjusts the voltage levels to suit UPP_WD2. The interface volt-
age level on the phone flash/test pad pattern is 2.78V and on the UPP WD2 end it is 1.8V.
The functionality of this interface should not affect the device boot into NORMAL, LOCAL
nor TEST modes. Phoenix tests can be performed through MBUS interface in the case of a
failure in FBUS interface. Flashing is not possible if there is a problem in FBUS.
MBUS
MBUS is a two wire RX and TX interface between UPP and UEM. From UEM the interface
continues to flash/test interface as a one wire interface. UEM also adjusts the voltage
levels. The interface voltage level on the phone flash/test pad pattern is 2.78V and on the
UPP WD2 end it is 1.8V. MBUS traffic between UPP WD2 and UEM can be tested with
PHOENIX (ST_MBUS_RX_TX_LOOP_TEST). Flashing is not possible if there is a problem in
MBUS.
Issue 1 09/2003
Company Confidential
Copyright  2003 Nokia Corporation.
Company Confidential
NEM-4
RF Troubleshooting
Page 6(b)-131