RM0440 Rev 4 623/2126
RM0440 Analog-to-digital converters (ADC)
724
Note: To convert a single channel, program a sequence with a length of 1.
It is not possible to have both discontinuous mode and continuous mode enabled: it is
forbidden to set both DISCEN=1 and CONT=1.
Injected channels cannot be converted continuously. The only exception is when an injected
channel is configured to be converted automatically after regular channels in continuous
mode (using JAUTO bit), refer to Auto-injection mode section)
.
21.4.15 Starting conversions (ADSTART, JADSTART)
Software starts ADC regular conversions by setting ADSTART=1.
When ADSTART is set, the conversion starts:
• Immediately: if EXTEN[1:0] = 00 (software trigger)
• At the next active edge of the selected regular hardware trigger: if EXTEN[1:0] is not
equal to 00
Software starts ADC injected conversions by setting JADSTART=1.
When JADSTART is set, the conversion starts:
• Immediately, if JEXTEN[1:0] = 00 (software trigger)
• At the next active edge of the selected injected hardware trigger: if JEXTEN[1:0] is not
equal to 00
Note: In auto-injection mode (JAUTO=1), use ADSTART bit to start the regular conversions
followed by the auto-injected conversions (JADSTART must be kept cleared).
ADSTART and JADSTART also provide information on whether any ADC operation is
currently ongoing. It is possible to re-configure the ADC while ADSTART=0 and
JADSTART=0 are both true, indicating that the ADC is idle.
ADSTART is cleared by hardware:
• In single mode with software regular trigger (CONT=0, EXTSEL=0x0)
– At any end of regular conversion sequence (EOS assertion) or at any end of
subgroup processing if DISCEN = 1
• In all cases (CONT=x, EXTSEL=x)
– After execution of the ADSTP procedure asserted by the software.
Note: In continuous mode (CONT=1), ADSTART is not cleared by hardware with the assertion of
EOS because the sequence is automatically relaunched.
When a hardware trigger is selected in single mode (CONT=0 and EXTSEL≠0x00),
ADSTART is not cleared by hardware with the assertion of EOS to help the software which
does not need to reset ADSTART again for the next hardware trigger event. This ensures
that no further hardware triggers are missed.
JADSTART is cleared by hardware:
• In single mode with software injected trigger (JEXTSEL = 0x0)
– At any end of injected conversion sequence (JEOS assertion) or at any end of
subgroup processing if JDISCEN = 1
• in all cases (JEXTSEL=x)
– After execution of the JADSTP procedure asserted by the software.
Note: When the software trigger is selected, ADSTART bit should not be set if the EOC flag is still
high.
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