ST STM32F205 series Reference Manual page 227

RM0033
•
DMA requests in Multi ADC mode:
In Multi ADC mode the DMA may be configured to transfer converted data in three
different modes. In all cases, the DMA streams to use are those connected to the ADC:
–
–
a)
b)
–
DMA mode 1: On each DMA request (one data item is available), a half-word
representing an ADC-converted data item is transferred.
In Triple ADC mode, ADC1 data are transferred on the first request, ADC2 data
are transferred on the second request and ADC3 data are transferred on the third
request; the sequence is repeated. So the DMA first transfers ADC1 data followed
by ADC2 data followed by ADC3 data and so on.
DMA mode 1 is used in regular simultaneous triple mode only.
Example:
Regular simultaneous triple mode: 3 consecutive DMA requests are generated
(one for each converted data item)
1st request: ADC_CDR[31:0] = ADC1_DR[15:0]
2nd request: ADC_CDR[31:0] = ADC2_DR[15:0]
3rd request: ADC_CDR[31:0] = ADC3_DR[15:0]
4th request: ADC_CDR[31:0] = ADC1_DR[15:0]
DMA mode 2: On each DMA request (two data items are available) two half-
words representing two ADC-converted data items are transferred as a word.
In Dual ADC mode, both ADC2 and ADC1 data are transferred on the first request
(ADC2 data take the upper half-word and ADC1 data take the lower half-word) and
so on.
In Triple ADC mode, three DMA requests are generated. On the first request, both
ADC2 and ADC1 data are transferred (ADC2 data take the upper half-word and
ADC1 data take the lower half-word). On the second request, both ADC1 and
ADC3 data are transferred (ADC1 data take the upper half-word and ADC3 data
take the lower half-word).On the third request, both ADC3 and ADC2 data are
transferred (ADC3 data take the upper half-word and ADC2 data take the lower
half-word) and so on.
DMA mode 2 is used in interleaved mode and in regular simultaneous mode (for
Dual ADC mode only).
Example:
Interleaved dual mode: a DMA request is generated each time 2 data items are
available:
1st request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]
2nd request: ADC_CDR[31:0] = ADC2_DR[15:0] | ADC1_DR[15:0]
Interleaved triple mode: a DMA request is generated each time 2 data items are
available
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]
DMA mode 3: This mode is similar to the DMA mode 2. The only differences are
that the on each DMA request (two data items are available) two bytes
RM0033 Rev 8
Analog-to-digital converter (ADC)
227/1378
255