Control A

Name:
CTRLA
Offset:
0x00 [ID-0000306e]
Reset:
0x0000
Access:
PAC Write-Protection, Write-Synchronised
Bit76543210
MODERUNSDTBYENABLESWRST
AccessR/WR/WR/WR/W
Reset0000

Bit 7 – MODE: Operating Mode

Operating Mode

This bit defines the operating mode of the USB.

ValueDescription
0 USB Device mode
1 USB Host mode

Bit 2 – RUNSDTBY: Run in Standby Mode

Run in Standby Mode

This bit is Enable-Protected.

ValueDescription
0 USB clock is stopped in standby mode.
1 USB clock is running in standby mode

Bit 1 – ENABLE: Enable

Enable

Due to synchronization there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The value written to CTRLA.ENABLE will read back immediately and the Synchronization status enable bit in the Synchronization Busy register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared when the operation is complete.

This bit is Write-Synchronized.

ValueDescription
0 The peripheral is disabled or being disabled.
1 The peripheral is enabled or being enabled.

Bit 0 – SWRST: Software Reset

Software Reset

Writing a zero to this bit has no effect.

Writing a '1' to this bit resets all registers in the USB, to their initial state, and the USB will be disabled.

Writing a '1' to CTRLA.SWRST will always take precedence, meaning that all other writes in the same write-operation will be discarded.

Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.

This bit is Write-Synchronized.

ValueDescription
0 There is no reset operation ongoing.
1 The reset operation is ongoing.