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HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide Description of the Application Interfaces
Issue 01 (2010-12-31)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
14
3.7 W_DISABLE# Signal
The W_DISABLE# signal is provided to allow users to disable wireless
communications add-in cards. When the W_DISABLE# signal is asserted, all radios
should be disabled. When the W_DISABLE# signal
is not asserted, the radio may
transmit signals if it is not disabled by other means such as software.
The W_DISABLE# signal is an active low signal with internal 100 kΩ pull-up resistor
that disables radio operation when being asserted (driven low) by the system.
The combination of the software state and W_DISABLE# assertion state must be
determined before the normal operation is resumed.
Table 3-10 lists this requirement
for W_DISABLE# and the software control setting. For example, the radio RF
operation remains disabled unless both the hardware and software are set to enable
the RF features of the card.
Table 3-9 W_DISABLE_N signal
Pins Name Description Direction to Module
20 W_DISABLE_N Close wireless communications Input
Table 3-10 Radio operational states
W_DISABLE# SW Control Setting* Radio Operation
High Enabled Enabled
High Disabled
Low Enabled
Low Disabled
Disabled
* This control setting is implementation specific; this column represents the collective intention of
the host software to manage radio operation.
z
If you do not turn off the radio manually, the radio will be on when the module is powered
on.
z
End users need to turn off the radio in some situations such as when being on an airplane.
z
According to Mini-PCIE specification, the radio must be turned off through hardware or
software. Nearly all PC companies comply with this specification.
3.8 LED_WWAN# Signal
The LED_WWAN signal of the EM820W can allow the voltage of 3.3 V and absorb
the current from 5 mA to 40 mA. According to the given circuit, in order to reduce the
current of the LED, a resistance of 1 kΩ must be placed in series with the LED.