Data Sheet

772
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
31.8 Register Description
Registers can be 8, 16, or 32 bits wide. Atomic 8-, 16-, and 32-bit accesses are supported. In addition, the 8-bit quarters
and 16-bit halves of a 32-bit register, and the 8-bit halves of a 16-bit register can be accessed directly.
Some registers are optionally write-protected by the Peripheral Access Controller (PAC). Write-protection is denoted by
Write-Protected property in each individual register description. Please refer to the “Register Access Protection” on page
746 section and the “PAC – Peripheral Access Controller” on page 41 for details.
Some registers require synchronization when read and/or written. Synchronization is denoted by the Write-Synchronized
or the Read-Synchronized property in each individual register description. Refer to “Synchronization” on page 101 for
details.
Some registers are enable-protected, meaning they can only be written when the USB is disabled. Enable-protection is
denoted by the Enable-Protected property in each individual register description.