Cordic Demo 8 by Busysoft
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:: CORDIC demo 8 ::
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8b education intro for ZX Spectrum 16k
Code: Busy soft
Create: 25.01.2025
Release: LoveByte 2025
This intro shows simplified CORDIC algorithm
intended for computing size of two-dimensed vector.
Source of the 8 byte routine
Input: C = coordinate X
B = coordinate Y
Output: C = result = SQR(X^2+Y^2)
ld a,c
L1: sub b
jr nc,L2
inc c
add c
L2: djnz L1
Register C contains X coordinate, what are increased by rotating vector or moving point on the circle.
Register B is counter of iterations or successive rotations, it is initialized to coordinate Y.
Register A holds bresenham's iterator used for computation. At begin, it is initialized to coordinate X.
To proper working of this simplified routine, a few mandatory conditions must be fulfilled:
(X^2+Y^2) < 65536 ... Since result is 8 bit only, we must make sure to not produce overflow
Y <= X .............. Number of iterations cannot be bigger than input coordinate X
Y > 0 ............... Number of iterations in priciple can be zero (then result is directly X)
but due to using DJNZ, zero means 256 iterations and it is not good
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