Datasheet

1004
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
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 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 and clearing TXVDIS in the UDP_TXVC
register.
40.6.3.8 Sending a Device Remote Wakeup
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
Before sending a K state to the host, MCK, UDPCK and the transceiver must be enabled. Then to enable the remote
wakeup feature, the RMWUPE bit in the UDP_GLB_STAT register must be enabled. To force the K state on the line, a
transition of the ESR bit from 0 to 1 has to be done in the UDP_GLB_STAT register. This transition must be
accomplished by first writing a 0 in the ESR bit and then writing a 1.
The K state is automatically generated and released according to the USB 2.0 specification.