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Instruction Prefetch and Fast Conversion

Question asked by Klaus on Oct 4, 2012
Latest reply on Oct 8, 2012 by Klaus
Hallo everyone,

I am working for a Company, which currently develops a new product. We currently evaluate the STM32F20x processors.
The processor shall convert voltage and current simultaneously and some other inputs.
We use the ADC in tripple mode. First for the voltage, the second for the current and the third for the rest of the inputs. Important is the fast conversion of current and voltage. The ADC is configured to use the DMA, which uses a double buffer. This all works fine so far. But there are two points that we have to clarify:
1. We had to deactivate the instruction prefetch as mentioned in latest errata. Otherwise the converted signal has too much noise. 10Bit is the minimum we want to see. The first question is, how much impact does it have when turning off the prefetch? It propable depends on the code, but can someone state a general percentage of performanceloss?
2. In the reference manual fast conversion is stated. We didnt see any reducement of the conversion time when setting ADC1-3 to 6 or 8 or 10. We do not get faster than 500ns per conversion. Should this be possible in triple mode including dma?

Thanks so far