Query on PDB in back to back operation mode

[PawanGupta]

Hi,

I am using S32k144 controller, and for ADC conversion I have selected PDB triggering. I want to understand the operation in the following Scenarios :

Case 1.: I set the value of PDB0 modulus as 10ms and all pre-trigger delay values as 100us and configured 8 ADC channels of ADC-0 with PDB Channel -0 for periodic conversions. So what will happen after the conversion of all 8 channels? Will PDB wait for modulus counter to reset and then trigger next round of conversion(i.e after 10ms) ? or Conversion will keep goes on continuously?

Case 2: If I want to use PDB0 CH0 for 8 ADC0 channels and PDB1 CH0 for 8 ADC1 channels, what configuration I need to do so that after PDB0 conversions automatically PDB1 will be triggered.

Case 3: If I want to use PDB0 CH0 for 8 ADC0 channels and PDB0 CH1 for the next 8 ADC0 channels, then will PDB0 CH1 will be triggered automatically after PDB0 CH0 conversions? or I have to trigger PDB0 CH1 manually?

Thanks,

Pawan

[PetrS · Accepted solution]

Hi,

1) The modulus value in the Modulus register (MOD) is used to reset the counter back to zero at the end of the count. If the Continuous Mode Enable (SC[CONT]) is set, then the counter will then resume a new count; otherwise, the counter operation will stop until the next trigger input event occurs.

2) if back-to-back mode is selected then always first pretrigger of the back-to-back connection chain has BB bit cleared and TOS set, thus a pretrigger's delay defines a time when this pretrigger is asserted. So you have to set such a delay, previous conversions of 8 ADC channels finished on channel 0 and so next back-to-back chain can start.

3) no, you have to define a delay as writen above.
Note: direct chaining between CH0 and CH1 of the PDB module is supported on S32K14xW variant only 

BR, Petr

[PawanGupta]

Thanks PetrS.

I have Enabled Continuous mode and selected back-to-back mode for 8 ADC on channels0.

So, after triggering PDB I am trying to read respective ADC result registers inside code's main() routine but values are not updating.

But, when I am reading the same registers in any ISR routine (eg. PDB or ADC isr) I am getting updated/fresh value.

Why is this behavior? Why I am not getting updated value if reading in regular main() routine?

[PetrS]

Hi,

this will be due to locked pretrigger from PDB. As written in chapter 46.4.1 PDB pre-trigger and trigger outputs of the RM...

So you need to read ADC results in time so this lock does not happen.

BR, Petr