249
8331B–AVR–03/12
Atmel AVR XMEGA AU
• Bit 4 – PULLRST: Pull during Reset
Setting this bit enables the pull-up on the USB lines to also be held when the device enters
reset. The bit will be cleared on a power-on reset.
• Bit 3 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write
this bit to zero when this register is written.
• Bit 2 – RWAKEUP: Remote Wake-up
Setting this bit sends an upstream resume on the USB lines if the bus is in the suspend state for
at least 5 ms.
• Bit 1 – GNACK: Global NACK
When this bit is set, the USB module will NACK all incoming transactions. Expect for a SETUP
packet, this prevents the USB module from performing any on-chip SRAM access, giving all
SRAM bandwidth to the CPU and/or DMA controller.
• Bit 0 – ATTACH: Attach
Setting this bit enables the internal D+ or D- pull-up (depending on the USB speed selection),
and attaches the device to the USB lines. Clearing this bit disconnects the device from the USB
lines.
20.13.3 STATUS – Status register
• Bit 7:4 – 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.
• Bit 3 – URESUME: Upstream Resume
This flag is set when an upstream resume is sent.
• Bit 2 – RESUME: Resume
This flag is set when a downstream resume is received.
• Bit 1 – SUSPEND: Bus Suspended
This flag is set when the USB linesare in the suspended state (the bus has been idle for at least
3ms).
• Bit 0 – BUSRST: Bus Reset
This flag is set when a reset condition has been detected (the bus has been driven to SE0 for at
least 2.5µs).
Bit 76543210
+0x02 – – – – URESUME RESUME SUSPEND BUSRST STATUS
Read/WriteRRRRRRRR
Initial Value 0 0 0 0 0 0 0 0
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