Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet

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Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181C–SAM-D21_Datasheet–07/2014

z

Serializer x Enable bits in the Control A register (CTRLA.SERENx). SYNCBUSY.SERENx is set to one while 
synchronization is in progress.The following registers require synchronization when read or written:

z

Data n registers (DATAn), Read-Synchronized when Serializer n is in Rx mode or Write-Synchronized when in Tx 
mode. SYNCBUSY.DATAn is set to one while synchronization is in progress.

Synchronization is denoted by the Read-Synchronized or Write-Synchronized property in the register description.

For debugging purposes, the I

2

S can be configured to loop back the Transmitter to the Receiver. Writing a one to the 

SERCTRLm.RXLOOP bit will configure SDm as input and the other SD as output. Both SD will be connected internally, 
so the transmitted data is also received. For instance, writing SERCTRL0.RXLOOP=1 will connect SD1 output to SD0 
input, or writing SERCTRL1.RXLOOP=1 will connect SD0 output to SD1 input.

RXLOOP=1 will connect the Transmitter output of the other Serializer to the Receiver input of the current Serializer. For 
the Loop-back Mode to work, the current Serializer must be configured as receiver and the other Serializer as transmitter. 

Writing a zero to SERCTRLm.RXLOOP will restore the normal behavior and connection between Serializer m and SDm 
pin input. As for other changes to the Serializer configuration, the Serializer m must be disabled before writing the 
SERCTRLm register to update SERCTRLm.RXLOOP.