Motorola DSP96002 - Manual (Page 574)

MOTOROLA DSP96002 USER’S MANUAL B-55
seedr d5,d4 ;y approx 1/sqrt(x) 1 1
fmpy.s d4,d4,d2 #.5,d7.s ;y*y, get .5 2 2
fmpy.s d5,d2,d2 #3.0,d3.s ;x*y*y, get 3.0 2 2
fmpy d4,d7,d2 fsub.s d2,d3 d3.s,d6.s ;y/2, 3-x*y*y 1 1
fmpy.s d2,d3,d4 d6.s,d3.s ;y/2*(3-x*y*y) 1 1
fmpy.s d4,d4,d2 ;y*y 1 1
fmpy.s d5,d2,d2 ;x*y*y 1 1
fmpy d4,d7,d2 fsub.s d2,d3 d3.s,d6.s ;y/2, 3-x*y*y 1 1
fmpy.s d2,d3,d4 ;y/2*(3-x*y*y) 1 1
--- ---
Totals: 11 11
B.1.30 Newton-Raphson Approximation for SQRT(x)
The approximation of sqrt(x) may be performed by using the Newton-Raphson iteration to first find 1.0/
sqrt(x). The sqrt(x) then can be approximated by x*(1.0/sqrt(x)).
Newton-Raphson Approximation Program ICycles
of SQRT(x) Words
seedr d5,d4 ;y approx 1/sqrt(x) 1 1
fmpy.s d4,d4,d2 #.5,d7.s ;y*y, get .5 2 2
fmpy.s d5,d2,d2 #3.0,d3.s ;x*y*y, get 3.0 2 2
fmpy d4,d7,d2 fsub.s d2,d3 d3.s,d6.s ;y/2, 3-x*y*y 1 1
fmpy.s d2,d3,d4 d6.s,d3.s ;y/2*(3-x*y*y) 1 1
fmpy.s d4,d4,d2 ;y*y 1 1
fmpy.s d5,d2,d2 ;x*y*y 1 1
fmpy d4,d7,d2 fsub.s d2,d3 d3.s,d6.s ;y/2, 3-x*y*y 1 1
fmpy.s d2,d3,d4 ;y/2*(3-x*y*y) 1 1
fmpy.s d5,d4,d4 ;x*(1/sqrt(x)) 1 1
--- ---
Totals: 12 12
B.1.31 Unsigned Integer Divide
The unsigned integer divide operation divides two 32 bit unsigned integers. The following code divides d0/
d2 with the resulting quotient in d0 and the remainder in d1.