pouët.net

::::::::::::::::::::
:: CORDIC demo 16 ::
::::::::::::::::::::

16 byte education intro for ZX Spectrum 16k

  Code: Busy soft
  Create: 26.01.2025
  Release: LoveByte 2025

This intro shows simplified CORDIC algorithm
intended for computing size of two-dimensed vector.


It is based on 8 byte routine from CORDIC demo 8
but the addtional preface is added to serve
the case of X < Y.

In this case, X and Y are swapped :)


Source code:

  Input: C = coordinate X
         B = coordinate Y

 Output: C = result = SQR(X^2+Y^2)

        ld      a,c
        cp      b
        jr      nc,L1
        ld      c,b
        ld      b,a

        ld      a,c
    L1: sub     b
        jr      nc,L2
        inc     c
        add     c
    L2: djnz    L1

Now whole routine takes 14 bytes length.

 The condition X >= Y disappeared, but all next conditions are still valid:

   (X^2+Y^2) < 65536 ... Since result is 8 bit only, we must make sure to not produce overflow
   X > 0 ........\____ Any coordinate can be zero (then result is directly another coordinate)
   Y > 0 ......../     but due to using DJNZ, zero means 256 iterations and it is still not good.

[ html | dos 80*25 | dos 80*50 | rez's ascii | amiga medres | amiga hires ]