SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
The ADC provides digital filters on the TRIPHI and TRIPLO signals to help prevent unwanted threshold trips. Each digital filter works on a window of FIFO samples (SAMPWIN) taken from the threshold comparator output. The filter output resolves to the majority value of the sample window, where majority is defined by the threshold (THRESH) value. If the majority threshold is not satisfied, the filter output remains unchanged. Figure 15-25 shows a block diagram of the PPB digital trip filter.
For proper operation, the value of THRESH must be greater than SAMPWIN / 2, and less than or equal to SAMPWIN.
A prescale function (CLKPRESCALE) determines the filter sampling rate. The filter FIFO captures one sample for every CLKPRESCALE cycles of SYSCLK. Old data from the FIFO is discarded.
The digital trip filters are disabled by default. To enable and configure the digital trip filters, write the desired values to the ADCPPBTRIPxFILCTL and ADCPPBTRIPxFILCLKCTL registers. Note that for SAMPWIN, THRESH and PRESCALE, the filter adds 1 to the value in the register field (for example, write 15 to SAMPWIN to enable a filter sample window of 16). To clear the FIFO and re-initialize the filter, write 1 to the FILINIT bit in the ADCPPBTRIPxFILCTL register.