Atmel Xplained Pro Evaluation Kit ATSAMD20-XPRO ATSAMD20-XPRO Data Sheet

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Atmel | SMART SAM D20 [DATASHEET]

Atmel-42129K–SAM-D20_datasheet–06/2014

ms

millisecond

µs

microsecond

ns

nanosecond

R/W

Read/Write accessible register bit. The user can read from and write to this bit. 

R

Read-only accessible register bit. The user can only read this bit. Writes will be ignored. 

W

Write-only accessible register bit. The user can only write this bit. Reading this bit will return an 
undefined value. 

BIT

Bit names are shown in uppercase. (Example ENABLE)

FIELD[n:m] 

A set of bits from bit n down to m. (Example: PINA[3:0] = {PINA3, PINA2, PINA1, PINA0}

Reserved

Reserved bits are unused and reserved for future use. For compatibility with future devices, always 
write reserved bits to zero when the register is written. Reserved bits will always return zero when 
read. 

PERIPHERALi

If several instances of a peripheral exist, the peripheral name is followed by a number to indicate the 
number of the instance in the range 0-n. PERIPHERAL0 denotes one specific instance. 

Reset

Value of a register after a power reset. This is also the value of registers in a peripheral after 
performing a software reset of the peripheral, except for the Debug Control registers.

SET/CLR

Registers with SET/CLR suffix allows the user to clear and set bits in a register without doing a read-
modify-write operation. These registers always come in pairs. Writing a one to a bit in the CLR 
register will clear the corresponding bit in both registers, while writing a one to a bit in the SET 
register will set the corresponding bit in both registers. Both registers will return the same value when 
read. If both registers are written simultaneously, the write to the CLR register will take precedence.