Huawei EM820W manual WDISABLE# Signal, LEDWWAN# Signal, Pins Name Description Direction to Module

HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide	Description of the Application Interfaces

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	3-9W_DISABLE_N signal
Pins		Name		Description		Direction to Module
20		W_DISABLE_N		Close wireless communications		Input
Table	3-10Radio operational states
W_DISABLE#			SW Control Setting*		Radio Operation
High			Enabled		Enabled
High			Disabled		Disabled
Low			Enabled
Low			Disabled

*This control setting is implementation specific; this column represents the collective intention of the host software to manage radio operation.

zIf you do not turn off the radio manually, the radio will be on when the module is powered on.

zEnd users need to turn off the radio in some situations such as when being on an airplane.

zAccording to Mini-PCIE specification, the radio must be turned off through hardware or software. Nearly all PC companies comply with this specification.

3.8LED_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.

Issue 01 (2010-12-31)	Huawei Proprietary and Confidential	14
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