35.7.4.6 Synchronization

Due to asynchronicity between the main clock domain and the peripheral clock domains, some SERCOM registers need to be synchronized when written ("Write-Synchronized") or read ("Read-Synchronized").

The following bits are synchronized when written:

  • The Software Reset bit in the CTRLA register (CTRLA.SWRST)
  • The Enable bit in the CTRLA register (CTRLA.ENABLE)
  • The Receiver Enable bit in the CTRLB register (CTRLB.RXEN)
  • The Data Length Enable bit and Data Length bits in the LENGTH register (LENGTH.LENEN, LENGTH.LEN)
Note: CTRLB.RXEN is write-synchronized somewhat differently than other registers. See the CTRLB register for details.

Required write synchronization is denoted by the "Write-Synchronized" property in the register description. If a write-synchronized register is written while a synchronization is ongoing, a Bus Error exception will be generated.