Perst# Signal - Huawei EM770 Product Specification

Table 3-12 LED_WWAN signal
Pins
42
This signal is used to display the state of WWAN. The reference circuit diagram is
shown in the following figure.
Figure 3-3 LED_WWAN# signal reference circuit diagram
Note:

3.2.7 PERST# Signal

The PERST# signal has an internal pull-up. The active low input is used to hard reset
the module.
The PERST# signal is de-asserted by the host to indicate that system power sources
are within the specified voltage tolerance and are stable. PERST# can be asserted
by the host when power is switched off and also can be used by the system to force a
hardware reset on the card. However, a hardware reset is not required during normal
operation and may only be used in case of module malfunction.
A hard reset of the module will result in a surprise removal of the module on the USB
controller and cause the operating system to unload the device drivers. This will lead
to a delay before the operating system discovers the device again. To avoid this delay,
the PERST# pin should not be used in normal operation or in standby mode.
Huawei Confidential: This documents is Huawei Proprietary and Confidential(NDA
Issue 1
Required).It may not be duplicated, neither distributed externally without
(2008-09-15)
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Name Description
LED_WWAN Active-low LED signal
for indicating the status
of the module.
1
kΩ
100 n
EM770
The wink mode of the LED can be customized by the demand of the client.
HUAWEI EM770 HSPA PC Embedded Module V100R001
LED_WWAN signal
Product Specification
Additional
Description
L: Light on
H: Light off
1 LED
kΩ
PC
Direction to
Module
Output
VCC
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