Datasheet

• Synchronization when written and read
• No synchronization
When executing an operation that requires synchronization, the Synchronization Busy bit in the Status
register (STATUS.SYNCBUSY) will be set immediately, and cleared when synchronization is complete.
If an operation that requires synchronization is executed while its busy bit is one, the operation is
discarded and an error is generated.
The following bits need synchronization when written:
• Software Reset bit in the Control A register (CTRLA.SWRST)
• Enable bit in the Control A register (CTRLA.ENABLE)
• All bits in the Data register (DATA)
• All bits in the Data Buffer register (DATABUF)
Write-synchronization is denoted by the Write-Synchronized property in the register description.
The following bits need synchronization when read:
• All bits in the Data register (DATA)
35.6.8 Additional Features
35.6.8.1 DAC as an Internal Reference
The DAC output can be internally enabled as input to the analog comparator. This is enabled by writing a
one to the Internal Output Enable bit in the Control B register (CTRLB.IOEN). It is possible to have the
internal and external output enabled simultaneously.
The DAC output can also be enabled as input to the Analog-to-Digital Converter. In this case, the output
buffer must be enabled.
35.6.8.2 Data Buffer
The Data Buffer register (DATABUF) and the Data register (DATA) are linked together to form a two-stage
FIFO. The DAC uses the Start Conversion event to load data from DATABUF into DATA and start a new
conversion. The Start Conversion event is enabled by writing a one to the Start Event Input bit in the
Event Control register (EVCTRL.STARTEI). If a Start Conversion event occurs when DATABUF is empty,
an Underrun interrupt request is generated if the Underrun interrupt is enabled.
The DAC can generate a Data Buffer Empty event when DATABUF becomes empty and new data can be
loaded to the buffer. The Data Buffer Empty event is enabled by writing a one to the Empty Event Output
bit in the Event Control register (EVCTRL.EMPTYEO). A Data Buffer Empty interrupt request is
generated if the Data Buffer Empty interrupt is enabled.
35.6.8.3 Voltage Pump
When the DAC is used at operating voltages lower than 2.5V, the voltage pump must be enabled. This
enabling is done automatically, depending on operating voltage.
The voltage pump can be disabled by writing a one to the Voltage Pump Disable bit in the Control B
register (CTRLB.VPD). This can be used to reduce power consumption when the operating voltage is
above 2.5V.
The voltage pump uses the asynchronous GCLK_DAC clock, and requires that the clock frequency be at
least four times higher than the sampling period.
SAM D21 Family
DAC – Digital-to-Analog Converter
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 965