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ADC Scan Control Register problem on MC56F84789

Question asked by Marco Aversa on Dec 23, 2015
Latest reply on Jan 11, 2016 by Marco Aversa

We're using ADC12 in independet parallel triggerd mode.

We want to acquire 6 samples on ADCB triggered via PDB1 (4 sync) syncing with ADC12_SCTRL in one PWM 8Khz cycle. At the end of ADC scan we want to have ADC ISR

 

Sample 0 -> ANB0

Sample 1 -> ANB0

Sample 2 -> ANB0

Sample 3 -> ANB0

Sample 4 -> ANB2

Sample 5 -> ANB6

 

PWM period 125us

PDB1 sync at 1us, 20us, 40us and 80us

 

ADC12_SCTRL = 0x00F0

 

Reading the reference manual we understand that :

ADC acquires the sample 0 and then it halts the scan

ADC acquires the sample 1 and then it halts the scan

ADC acquires the sample 2 and then it halts the scan

ADC acquires the samples 3-4-5 in continuous mode.

After this triggered the ADC end of scan event ISR.

 

In our case instead at every sync pulse the ADC acquires always the sample and halted. The samples 3-4-5 are not acquired in one sync. We have the ISR trigger every 6 sync, verfied with the oscilloscope.

 

We tried to change ADC12_SCTRL but nothing changed.

We note that when you set the "scan control" bit for sample 0 "as pause", the remaining scan control bit are not managed. Basically, in any way, we can't to group multiple samples in a single sync pulse.

 

We use the AN4608 and the AN4583 as reference. The difference in the application note AN4608  is that it 's used the scan control but in simultaneous parallel triggred mode.

 

ADC12_Setup.jpg

 

Thanx for any help!

Marco

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