Sierra Wireless MC5725 Hardware Integration Manual page 63

Rev 1.9.1 Feb.09
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
The module uses the USB standard Suspend and Resume
functions (described further) to control the sleep and wakeup
states. For detailed specifications of Resume and Suspend,
refer to Universal Serial Bus Specification, Rev 2.0.
Suspending
The module supports USB Suspend mode.
When the module enters suspend mode, it shuts down the
USB clock to save power.
While in the suspend state:
• The module provides power to the D+/‐ interface to signal
its current state to the host device.
• The host must maintain the VCC_3V3 voltage.
Refer to Universal Serial Bus Specification, Rev 2.0 for critical
timing parameters for the suspend state.
Resume
USB activity may be resumed by either the USB host or by the
module.
If the host initiates USB activity:
The USB transceiver detects the change in bus activity and
1.
triggers the USB_RESUME interrupt to the moduleʹs
processor.
The module then enables its USB clock and responds to the
2.
host.
If the module initiates USB communication (Remote Wakeup):
1. The module enables its USB clock.
The module enables the USB transceiver.
2.
The module sends the resume signal for at least 20 ms.
3.
Refer to Universal Serial Bus Specification, Rev 2.0 for critical
timing parameters for the resume state.
Host USB driver requirements
The USB driver on the host device must meet these critical
requirements:
The host USB driver must support remote wakeup, resume,
•
and suspend operations as described in Universal Serial Bus
Specification, Rev 2.0.
The host USB driver must support serial port emulation.
•
The module implements both 27.010 multiplexing and USB‐
CDC.
• When the host doesn't have any valid data to send, the host
USB driver should NOT send any SOF tokens (start‐of‐
Proprietary and Confidential
Host / Module Interfaces
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