User Guide

RH-51/52, RH-67/68 Company Confidential
6(a) - Baseband Troubleshooting Nokia Customer Care
Page 14 © 2004 Nokia Corporation. Issue 3 09/2004
Baseband serial interface troubleshooting
CBUS
CBUS is a three-wire serial interface between the main baseband components. The bus
consists of data, clock and bus_enable signals. In RH-51/52, RH-67/68 the bus is con-
nected between UPP_WD2, UEME and ZOCUS. UPP_WD2 takes care of controlling the
traffic on the bus.
If the interface is faulty from the UPP_WD2’s end, the phone does not boot properly as
powering configurations do not work. Traffic on the bus can be monitored at the follow-
ing test point and pins.
• CBusClk UPP_WD2 side of R106 pin
• CBusEN1X J378 Pad
• CBusDA J377 Pad
The pads and pin are shown below.
Figure 7: CBUS test points