Basically, INVL is set to 1, if ADC operation is suspended intentionally/accidentally.
One of reason is due to Priority conversion operation, as you mentioned.
If the ADC operation with Level1 priority is required during ADC operation with Level2 priority, the ADC operation with Level2 priority is suspended, and INVL is set to 1 for the ADC operation with Level2 priority. And, the ADC operation with Level2 priority is resumed and completed after the ADC operation with Level1 priority completion, then INVL is cleared.
As the other case, when user stops ADC during its operation, INVL is set to 1.
Anyway, please discard the ADC result data with INVL=1.
Thank you for your answer.
I thought that data might not be written to the FIFO when the conversion was interrupted, but it was an operation like accessing the FIFO even when AD conversion was interrupted.
I understood this issue.