24.8.1 Control A

Name:	CTRLA
Offset:	0x00
Reset:	Loaded from NVM User Row at start-up
Property:	PAC Write-Protection, Write-Synchronized


Bit	7	6	5	4	3	2	1	0
	ALWAYSON					WEN	ENABLE
Access	R/W					R/W	R/W
Reset	0					0	0

Bit 7 – ALWAYSON Always-On

This bit allows the WDT to run continuously. After being set, this bit cannot be written to '0', and the WDT will remain enabled until a power-on Reset is received. When this bit is '1', the Control A register (CTRLA), the Configuration register (CONFIG) and the Early Warning Control register (EWCTRL) will be read-only, and any writes to these registers are not allowed.

Writing a '0' to this bit has no effect.

This bit is not Enable-Protected.

This bit is loaded from NVM User Row at start-up. Refer to NVM User Row Mapping.

Value	Description
0	The WDT is enabled and disabled through the ENABLE bit.
1	The WDT is enabled and can only be disabled by a power-on reset (POR).

Bit 2 – WEN Watchdog Timer Window Mode Enable

This bit enables Window mode. It can only be written if the peripheral is disabled unless CTRLA.ALWAYSON=1. The initial value of this bit is loaded from Flash Calibration.

This bit is loaded from NVM User Row at startup. Refer to NVM User Row Mapping.

Value	Description
0	Window mode is disabled (normal operation).
1	Window mode is enabled.

Bit 1 – ENABLE Enable

This bit enables or disables the WDT. It can only be written if CTRLA.ALWAYSON=0.

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