Power And Reset Handshaking Protocols - Sierra Wireless MC5720 Hardware Integration Manual

USB activity is resumed either by the USB host or by the modem. The USB
controller automatically detects the USB host resuming bus activity, even if the
48 MHz oscillator is disabled. This is indicated by the resume interrupt. When
the resume interrupt is detected, the modem must re-enable the 48 MHz oscillator
for the USB controller. If the modem is initiating the resume via remote wakeup,
the 48 MHz oscillator must first be re-enabled. Then the modem directs the USB
controller to resume USB activity by writing the RESUME command (0x02) to
USB_CONTROL_CMD.

POWER and RESET handshaking protocols

This section describes the power-up and power-down on the embedded module.
Power on
The power-on sequence is shown in on page 31. The letters in the figure
correspond to these events:
A. VCC_3V3 is asserted,.
B. The host deasserts the W_Disable# signal to power up the module.
Power off
The power off sequence is shown in on page 31. The letters in the figure
correspond to these events:
A. The host sends the module the AT command to prepare for power down.
B. The module performs any necessary housekeeping functions and then
C. W_Disable# should be asserted by the host.
Rev 1.2
A p r - 0 5
(See the EM AT Command Reference).
responds to the message.
P r o p r i e t a r y a n d c o n f i d e n t i a l
H o s t I n t e r f a c e
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