"TMS320C55x DSP Library DSPLIB Programmer's Reference"

log_2log_2Base 2 LogarithmFunctionushort oflag = log_2 (DATA *x, LDATA *r, ushort nx)(defined in log_2.asm)Argumentsx[nx]r[nx]nxoflagPointer to input vector of size nx.Pointer to output data vector (Q31 format) of size nx.Length of input and output data vectorsOverflow flag. If oflag = 1, a 32-bit overflow has occurred. If oflag = 0, a 32-bit overflow has not occurred.DescriptionComputes the log base 2 of elements of vector x using Taylor series.Algorithm for (i 0; i nx; i ) y(i) log 12x(i) where 0 x(i) 1Overflow Handling MethodologyNo scaling implemented for overflow preventionSpecial Requirements noneImplementation Notes y = 1.4427 * ln(x) with x = M(x)*2^P(x) = M*2^Py = 1.4427 * (ln(M) + ln(2)*P)y = 1.4427 * (ln(2*M) + (P–1)*ln(2))y = 1.4427 * (ln((2*M–1)+1) + (P–1)*ln(2))y = 1.4427 * (f(2*M–1) + (P–1)*ln(2))with f(u) = ln(1+u).We use a polynomial approximation for f(u) :f(u) = (((((C6*u+C5)*u+C4)*u+C3)*u+C2)*u+C1)*u+C0for 0