33.3.1.3 SYNCH Character

The SYNCH character has eight bits and follows the regular UPDI frame format. It has a fixed value of 0x55. The SYNCH character has two main purposes:
  1. It acts as the enabling character for the UPDI after a disable.
  2. It is used by the Baud Rate Generator to set the baud rate for the subsequent transmission. If an invalid SYNCH character is sent, the next transmission will not be sampled correctly.