Data Sheet

Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181G–SAM-D21_Datasheet–09/2015

z Bit 5 – DNRSM: Down Resume Interrupt Flag

This flag is cleared by writing a one to the flag.

This flag is set when the USB has sent a Down Resume and will generate an interrupt if INTENCLR/SET.DRSM is

one.

Writing a zero to this bit has no effect.

z Bit 4 – WAKEUP: Wake Up Interrupt Flag

This flag is cleared by writing a one.

This flag is set when:

z The host controller is in suspend mode (SOFE is zero) and an upstream resume from the device is

detected.

z The host controller is in suspend mode (SOFE is zero) and an device disconnection is detected.

z The host controller is in operational state (VBUSOK is one) and an device connection is detected.

In all cases it will generate an interrupt if INTENCLR/SET.WAKEUP is one.

Writing a zero to this bit has no effect.

z Bit 3 – RST: Bus Reset Interrupt Flag

This flag is cleared by writing a one to the flag.

This flag is set when a Bus “Reset” has been sent to the Device and will generate an interrupt if INTEN-

CLR/SET.RST is one.

Writing a zero to this bit has no effect.

z Bit 2 – HSOF: Host Start-of-Frame Interrupt Flag

This flag is cleared by writing a one to the flag.

This flag is set when a USB “Host Start-of-Frame” in Full Speed or a keep-alive in Low Speed has been sent

(every 1 ms) and will generate an interrupt if INTENCLR/SET.HSOF is one.

The value of the FNUM register is updated.

Writing a zero to this bit has no effect.

z Bits 1:0 – Reserved

These bits are unused and reserved for future use. For compatibility with future devices, always write these bits to

zero when this register is written. These bits will always return zero when read.