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M0A21/M0A23 Series
May 06, 2022
Page
685
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
ADC peripheral Clock Generator
The maximum sampling rate is up to 500K SPS. The ADC has four clock sources selected by
ADCSEL
(CLKSEL2[21:20]), the ADC peripheral clock frequency is divided by an 8-bit pre-scalar with the
following formula:
ADC peripheral
clock frequency = (ADC peripheral
clock source frequency) / (1)
;
where the 8-bit ADCDIV is located in register CLKDIV0[23:16].
11
10
01
00
Reserved
HXT
HIRC
ADCSEL (CLKSEL2[21:20])
ADCCKEN(APBCLK0[28])
ADCCLK
1/( 1)
ADCDIV(CLKDIV0[23:16])
PCLK1
Legend:
HXT
= High-Speed External clock signal
HIRC = High-Speed Internal clock signal
Figure 6.19-2 ADC Peripheral Clock Control
Single Mode
In Single mode, A/D conversion is performed only once on the specified single channel. The operations
are as follows:
1. A/D conversion will be started when the ADST bit of ADC_ADCR register is set to 1 by
software or external trigger input.
2. When A/D conversion is finished, the result is stored in the ADC data register corresponding
to the channel.
3. The ADF bit of ADC_ADSR0 register will be set to 1. If the ADIE bit of ADC_ADCR register is
set to 1, the ADC interrupt will be asserted.
4. The ADST bit remains 1 during A/D conversion. When A/D conversion ends, the ADST bit is
automatically cleared to 0 and the A/D converter enters idle state.
Note 1:
If software enables more than one channel in Single mode, only the channel with the smallest
number will be selected and the other enabled channels will be ignored.
Note 2:
If ADST bit is cleared to 0 before ADC conversion done, ADC cannot finish the current
conversion, the BUSY bit will be cleared to 0 immediately and A/D converter enters idle state directly.