Setting FIR Length - 2025.2 English

The minimum FIR length is set to 1.

Single Rate FIRs have no restriction placed on the FIR length selection.

However, rate-changing FIRs require each of the individual kernels to operate on a FIR length divisible by the Decimation or Interpolation factor, imposing limits on the FIR length, e.g., TP_FIR_LEN % TP_DECIMATE_FACTOR == 0 or TP_FIR_LEN % TP_INTERPOLATE_FACTOR == 0.

In SSR modes, see Super Sample Rate - Operation Modes; coefficients are distributed equally across all output paths. As a result, the total number of FIRs coefficients must be divisible by number of paths, i.e., TP_FIR_LEN % (TP_SSR) == 0. For rate-changing FIRs this raises additional limits on the FIR length, where FIR length can be described by e.g.: TP_FIR_LEN % (TP_SSR * TP_PARA_INTERP_POLY * TP_PARA_DECI_POLY) == 0.