Datasheet

281
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
22.18 Registers
22.18.1 USB Device General Registers
• Bits 7:4 - Reserved
The value read from these bits is always 0. Do not set these bits.
• Bit 3 - RSTCPU - USB Reset CPU bit
Set this bit to 1 by firmware in order to reset the CPU on the detection of a USB End of Reset signal (without
disabling the USB controller and Attached state). This bit is reset when the USB controller is disabled, but is not
affected by the CPU reset generated after a USB End of Reset (remains enabled).
• Bit 2 - LSM - USB Device Low Speed Mode Selection
When configured USB is configured in device mode, this bit allows to select the USB the USB Low Speed or Full
Speed Mod.
Clear to select full speed mode (D+ internal pull-up will be activate with the ATTACH bit will be set).
Set to select low speed mode (D- internal pull-up will be activate with the ATTACH bit will be set). This bit has no
effect when the USB interface is configured in HOST mode.
• Bit 1- RMWKUP - Remote Wake-up Bit
Set to send an “upstream-resume” to the host for a remote wake-up (the SUSPI bit must be set).
Cleared by hardware when signalling finished. Clearing by software has no effect.
See Section 22.10, page 273 for more details.
• Bit 0 - DETACH - Detach Bit
Set to physically detach de device (disconnect internal pull-up on D+ or D-).
Clear to reconnect the device. See Section 22.9, page 272 for more details
Bit 76543 2 1 0
----RSTCPU
LSM RMWKUP DETACH UDCON
Read/WriteRRRRRR/WR/WR/W
Initial Value00000 0 0 1