SPRUIV7B May 2022 – September 2023 AM620-Q1 , AM623 , AM625 , AM625-Q1 , AM625SIP
Sigma-delta Sinc filtering is achieved by the combination of PRU hardware and firmware. PRU hardware provides hardware integrators that do the accumulation part of Sinc filtering, while the differentiation part is done in firmware.
The integrator serves to count the number of 1’s per clock event. Each channel has three cascaded counters, which are the accumulators for the Sinc3 filter. Each counter is 28 bits, giving a maximum count of 268,435,456. Each channel has a free running rollover clock counter. This sample counter updates the count value on the effective clock event for that channel. Each channel also contains a programmable counter compare block, and the compare register has a size of 8 bits. However, the minimum value is 4 and maximum value is 256 due to the 28-bit accumulator. Once sample counter compare value is reached, the shadow register copy is updated and the shadow register copy flag is set.
Features of the integrators in PRUs SD Demodulator: