Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

1018

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 is set. This interrupt may be used to wake up the core, enable PLL and 

main oscillators and configure clocks. 

: 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.

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

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

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

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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.