Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet

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SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]

11063K–ATARM–05-Nov-13

In suspend mode, a resume event on the USB bus line is detected asynchronously, transceiver and clocks are disabled
(however the pull-up shall not be removed).

Once the resume is detected on the bus, the WAKEUP signal in the UDP_ISR is set. It may generate an interrupt if the
corresponding bit in the UDP_IMR register is set. This interrupt may be used to wake up the core, enable PLL and main
oscillators and configure clocks. 

Warning: Read, write operations to the UDP registers are allowed only if MCK is enabled for the UDP peripheral. MCK
for the UDP must be enabled before clearing the WAKEUP bit in the UDP_ICR register and clearing TXVDIS in the
UDP_TXVC register.

In Suspend state it is possible to wake up the host sending an external resume. 



The device must wait at least 5 ms after being entered in suspend before sending an external resume.



The device has 10 ms from the moment it starts to drain current and it forces a K state to resume the host.



The device must force a K state from 1 to 15 ms to resume the host

To force a K state to the bus (DDM at 3.3V and DDP tied to GND), it is possible to use a transistor to connect a pull-up on
DDM. The K state is obtained by disabling the pull-up on DDP and enabling the pull-up on DDM. This should be under
the control of the application.

3V3

PIO

1.5 K

0: Force Wake UP (K State)
1: Normal Mode

DM