"TMS320C55x DSP Library DSPLIB Programmer's Reference"

iircas4nxoflagNumber of elements of input and output vectorsOverflow flag. If oflag = 1, a 32-bit overflow has occurred If oflag = 0, a 32-bit overflow has not occurredDescriptionComputes a cascade IIR filter of nbiq biquad sections. Each biquad section isimplemented using Direct-form II. All biquad coefficients (4 per biquad) arestored in vector h. The real data input is stored in vector x. The filter outputresult is stored in vector r.This function retains the address of the delay filter memory d containing theprevious delayed values to allow consecutive processing of blocks. This functionis more efficient for block-by-block filter implementation due to the C-callingoverhead. However, it can be used for sample-by-sample filtering (nx = 1).Algorithm(for biquad)d(n) x(n) a1*d(n 1) a2*d(n 2)y(n) d(n) b1*d(n 1) b2*d(n 2)Overflow Handling MethodologyNo scaling implemented for overflow prevention.Special Requirements noneImplementation Notes noneExampleBenchmarksSee examples/iircas4 subdirectory(preliminary)Cycles † Core: nx * (2 + 3 * nbiq)Overhead: 44Code size(in bytes)122† Assumes all data is in on-chip dual-access RAM and that there is no bus conflict due to twiddletable reads and instruction fetches (provided linker command file reflects those conditions).Function Descriptions4-57