"TMS320C55x DSP Library DSPLIB Programmer's Reference"

convol1DescriptionComputes the real convolution of two real vectors x and h, and places theresults in vector r. This function utilizes the dual-MAC capability of the C55xto process in parallel two output samples for each iteration of the inner functionloop. It is, therefore, roughly twice as fast as CONVOL, which implements onlya single-MAC approach. However, the number of output samples (nr) must beeven. Typically used for block FIR filter computation when there is no need toretain an input delay buffer. This function can also be used to implement singlesampleFIR filters (nr = 1) provided the input delay history for the filter is maintainedexternal to this function. In-place computation (r = x) is allowed, but beaware that the r output vector is shorter in length than the x input vector; therefore,r will only overwrite the first nr elements of the x.Algorithmnh1r[j] h[k] x[j k]k00 j nrOverflow Handling MethodologyNo scaling implemented for overflow prevention.Special Requirementsnr must be an even value.The vector h[nh] must be located in internal memory since it is accessedusing the C55x coefficient bus, and that bus does not have access to externalmemory.Implementation Notes Figure 4–7, Figure 4–8, and Figure 4–9 show the x, r, and h arrays as theyappear in memory.Figure 4–7. x Array in Memoryx(0)x(1)•x(nr+nh–2)x(nr+nh–1)lowest memory addresshighest memory address4-26