"TMS320C55x DSP Library DSPLIB Programmer's Reference"

iircas5iircas5FunctionArgumentsCascaded IIR Direct Form II (5 Coefficients per Biquad)ushort oflag = iircas5 (DATA *x, DATA *h, DATA *r, DATA *dbuffer, ushort nbiq,ushort nx)(defined in iircas5.asm)x [nx]Pointer to input data vector of size nxh[5*nbiq]r[nx]Pointer to filter coefficient vector with the followingformat:h = a11 a21 b21 b01 b11 ... a1i a2i b2i b0i b1iwhere i is the biquad index a21 is the a2 coefficient ofbiquad 1). Pole (recursive) coefficients = a. Zero(non-recursive) coefficients = bPointer to output data vector of size nx. r can be equalthan x.dbuffer[2*nbiq] Pointer to address of delay line d. Each biquad has 2delay line elements separated by nbiq locations in thefollowing format:d1(n–1), d2(n–1),..di(n–1) d1(n–2), d2(n–2)...di(n–2)where i is the biquad index(d2(n–1) is the (n–1)thdelay element for biquad 2).nbiqIn the case of multiple-buffering schemes, this arrayshould be initialized to 0 for the first block only. Betweenconsecutive blocks, the delay buffer preservesthe previous r output elements needed.Memory alignment: this is a circular buffer and muststart in a k-bit boundary(that is, the k LSBs of thestarting address must be zeros) where k = log2(2*nbiq).Number of biquadsnxoflagNumber 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 (5 per biquad) arestored in vector h. The real data input is stored in vector x. The filter outputresult is stored in vector r.4-58