Datasheet

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Symbol Description
MHz 1 MHz = 10
6
Hz = 1,000,000 Hz
GHz 1 GHz = 10
9
Hz = 1,000,000,000 Hz
s second
ms millisecond
µs microsecond
ns nanosecond
43.4 Registers and Bits
Table 43-4. Register and Bit Mnemonics
Symbol Description
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.
Reserved bit field values must not be written to a bit field. A reserved value will not be
read from a read-only bit field.
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 ‘1’
to a bit in the CLR register will clear the corresponding bit in both registers, while
writing a ‘1’ 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.
SAM D21 Family
Conventions
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 1176