RM0090: Reference manual - STMicroelectronics

RM0090 Analog-to-digital converter (ADC)
If the CONT bit is set on ADC1, ADC2 and ADC3, the selected regular channels of all ADCs
are continuously converted.
In this mode a DMA request is generated each time 2 data items are available, (if the
DMA[1:0] bits in the ADC_CCR register are equal to 0b10). The request first transfers the
first converted data stored in the lower half-word of the ADC_CDR 32-bit register to SRAM,
then it transfers the second converted data stored in ADC_CDR’s upper half-word to SRAM.
The sequence is the following:
● 1st request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]
● 2nd request: ADC_CDR[31:0] = ADC1_DR[15:0] | ADC3_DR[15:0]
● 3rd request: ADC_CDR[31:0] = ADC3_DR[15:0] | ADC2_DR[15:0]
● 4th request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0], ...
Figure 47. Interleaved mode on 1 channel in continuous conversion mode: triple
ADC mode
ADC1
ADC2
ADC3
Trigger
11.9.4 Alternate trigger mode
This mode can be started only on an injected group. The source of external trigger comes
from the injected group multiplexer of ADC1.
Note: Regular conversions can be enabled on one or all ADCs. In this case the regular
conversions are independent of each other. A regular conversion is interrupted when the
ADC has to perform an injected conversion. It is resumed when the injected conversion is
finished.
The time interval between 2 trigger events must be greater than or equal to 1 ADC clock
period. The minimum time interval between 2 trigger events that start conversions on the
same ADC is the same as in the single ADC mode.
Dual ADC mode
CH0
6 ADCCLK
cycles
CH0
CH0
End of conversion on ADC1
DMA request every 2 conversions
CH0
CH0
...
CH0
...
...
End of conversion on ADC3
End of conversion on ADC2
● When the 1st trigger occurs, all injected ADC1 channels in the group are converted
● When the 2nd trigger occurs, all injected ADC2 channels in the group are converted
● and so on
A JEOC interrupt, if enabled, is generated after all injected ADC1 channels in the group
have been converted.
CH0
CH0
CH0
Sampling
Conversion
ai16058
Doc ID 018909 Rev 3 282/1416