Atmel SAM9X25, Manual

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42.5 Product Dependencies
42.5.1 Power Management
The ADC Controller is not continuously clocked. The programmer must first enable the ADC
Controller MCK in the Power Management Controller (PMC) before using the ADC Controller.
However, if the application does not require ADC operations, the ADC Controller clock can be
stopped when not needed and restarted when necessary. Configuring the ADC Controller does
not require the ADC Controller clock to be enabled.
42.5.2 Interrupt Sources
The ADC interrupt line is connected on one of the internal sources of the Interrupt Controller.
Using the ADC interrupt requires the AIC to be programmed first.
42.5.3 Analog Inputs
The analog input pins can be multiplexed with PIO lines. In this case, the assignment of the ADC
input is automatically done as soon as the corresponding channel is enabled by writing the reg-
ister ADC_CHER. By default, after reset, the PIO line is configured as input with its pull-up
enabled and the ADC input is connected to the GND.
42.5.4 I/O Lines
The pin ADTRG may be shared with other peripheral functions through the PIO Controller. In
this case, the PIO Controller should be set accordingly to assign the pin ADTRG to the ADC
function.
42.5.5 Timer Triggers
Timer Counters may or may not be used as hardware triggers depending on user requirements.
Thus, some or all of the timer counters may be unconnected.
42.5.6 Conversion Performances
For performance and electrical characteristics of the ADC, see the product DC Characteristics
section.
42.6 Functional Description
42.6.1 Analog-to-digital Conversion
The ADC uses the ADC Clock to perform conversions. Converting a single analog value to a 10-
bit digital data requires Tracking Clock cycles as defined in the field TRACKTIM of the
“ADC
Mode Register” on page 974 and Transfer Clock cycles as defined in the field TRANSFER of the
same register. The ADC Clock frequency is selected in the PRESCAL field of the Mode Register
(ADC_MR). The tracking phase starts during the conversion of the previous channel. If the track-
ing time is longer than the conversion time, the tracking phase is extended to the end of the
previous conversion.
The ADC clock range is between MCK/2, if PRESCAL is 0, and MCK/512, if PRESCAL is set to
255 (0xFF). PRESCAL must be programmed in order to provide an ADC clock frequency
according to the parameters given in the product Electrical Characteristics section.
Table 42-2. Peripheral IDs
Instance ID
ADC 19