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G700-U10 Smartphone
Maintenance Manual
10 Circuit and Failure Analysis
Issue 1.0 (2013-07-22)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
83
Troubleshooting Process
Figure 10-57
Troubleshooting USB detection failures
USB failure
Is the USB port
properly soldered?
Resolder the USB port
Y
Are the surrounding
components of the USB port
properly functioning?
Resolder or replace the
surrounding
components
Y
N
N
Resolder or
replace U401
Circuit Signals
Table 10-19
Circuit signals of this section
Signal
Description
Reference Value or Waveform
VBUS
USB power supply
The voltage is 3.3 V.
USB_DM USB data (+)
High-speed digital pulse signal
USB_DP
USB data (–)
High-speed digital pulse signal
KCOL0
USB download triggering
signal
When KCOL0 is grounded, the system enters
USB download mode.