Huawei U8860 Maintenance Manual page 60

U8860
Maintenance Manual
USIM interface of the MSM8255
Signal
USIM_IO
USIM_RST
USIM_CLK
USIM_VCC
After is phone is powered on, it will detect the SIM card. If the SIM card is found, it will start
data communication, and the preceding pins will perform power clock and data transmission.
If the SIM card is not found, the system does not detect SIM card status. Therefore, it does not
support hot swap.
Troubleshooting process
Failure: The USIM card cannot be detected.
Solution: Firstly, check whether the software is faulty or the USIM card is damaged. If the
card is not damaged, perform the following procedure.
Issue 1.0 (2011-11-14)
Description
SIM data line
SIM reset signal
SIM clock
SIM power supply, 1.8 V/3.0 V
No USIM card is found.
Is the USIM card
socket normal?
Y
Is D1601
short-circuited?
(Pin3 and Pin6
is ground.)
N
Are the power-supply pin
and signal pin normal?
Y
Re-solder or
replace the U301.
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9 Principles and Troubleshooting
N
Re-solder or
replace the USIM
card socket J1601.
Y
Replace D1601.
After the cabling
problem is
N
excluded, re-
solder or replace
the U301.
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