A while ago I made Floatlib, an app that contained a bunch of Z80 single-precision floating point routines (as well as a few other helpful routines). My intent was for my own on-calc programming, so it includes in-app documentation. Anyways, I got bored and decided to make a program that draws the Mandelbrot Set as kind of an example. The program requires Floatlib to be on your calc, but the source is:
#include "header.z80"
cx = vars
cy = vars+4
delta= vars+8
zx = vars+12
zy = vars+16
zx2 = vars+20
zy2 = vars+24
x = vars+28
y = vars+29
bufptr=vars+30
mask = vars+32
lcd_y= vars+33
tmp = vars+34
gbuf = 9340h
maxiter=16
start:
in a,(2)
add a,a
sbc a,a
and 3
out (20h),a
call init ;initialize keyboard, LCD, variables
forx:
ld a,64 ;set Y counter to 64
ld (y),a
ffmov(cy_init,cy)
ffmov(delta_init,delta)
fory:
in a,(1) ;poll the keyboard for [Clear]
and 40h
ret z
in a,(4) ;poll for [ON]
and 8
ret z
ffmov(cx,zx)
ffmov(cy,zy)
fmul(zx,zx,zx2)
fmul(zy,zy,zy2)
ld a,maxiter
jp endwhile
startwhile:
fmul(zx,zy,zy)
ld hl,zy+3 ;multiply zy by 2 by incrementing the exponent. No worries of overflow, so we can do this cheaply
inc (hl)
fadd(cy,zy,zy)
fsub(zx2,zy2,zx)
fadd(cx,zx,zx)
fmul(zx,zx,zx2)
fmul(zy,zy,zy2)
endwhile:
dec a
jr z,plotcalc
fadd(zx2,zy2,tmp)
;fcmp(tmp,four)
ld h,a
ld a,(tmp+3) ;check if tmp>=4. This happens if and only if the exponent of tmp is 82h or higher.
cp 82h
ld a,h
jr c,startwhile
plotcalc:
or a ;plot the pixel if counter reached zero
ld a,(mask)
ld hl,(bufptr)
jr nz,$+5
or (hl)
jr $+4
cpl
and (hl)
ld (hl),a
out (17),a
ld de,12
add hl,de
ld (bufptr),hl
fadd(cy,delta,cy)
ld hl,y
dec (hl)
jp nz,fory
fadd(cx,delta,cx)
ld hl,(bufptr)
ld a,(mask)
dec h
dec h
dec h
rrca
ld (mask),a
jr nc,+_
inc l
ld a,(lcd_y)
inc a
out (16),a
cp 2Ch
ld (lcd_y),a
_:
ld (bufptr),hl
ld hl,x
dec (hl)
jp nz,forx
ret
init:
di
ld a,80h ;Program the LCD to move the index to the top
out (16),a
;ld a,80h ;load the mask for the pixel data. Commented since 'a' is already 80h
ld (mask),a
ld hl,gbuf ;load the ptr to the actual pixel data
ld (bufptr),hl
ld a,96 ;set X counter
ld (x),a
ld hl,(cx_init) \ ld (cx),hl ;load the starting value for cx
ld hl,(cx_init+2) \ ld (cx+2),hl
ld a,$FD ;Program the keyboard to only poll for keys in the [Enter] through [Clear] range
out (1),a
ld a,20h
ld (lcd_y),a
out(16),a
xor a
ld hl,gbuf
ld (hl),a
ld de,gbuf+1
ld bc,767
ldir
ret
cx_init:
.db $00,$00,$80,$81 ;-2.0
; .db $00,$00,$80,$80 ;-1.0
; .db $51,$D6,$56,$7E ;.41960384
; .db $00,$00,$A0,$80 ;-1.25
cy_init:
; .db $00,$00,$80,$81 ;-2.0
.db $00,$00,$80,$80 ;-1.0
; .db $7C,$AA,$48,$7D ;.19596284
; .db $00,$00,$80,$7E ;-.25
;48aa7C
delta_init:
; .db $00,$00,$00,$7C ;.0625
.db $00,$00,$00,$7B ;.03125
; .db $1b,$29,$1d,$73 ;.00007494
; .db $00,$00,$00,$79 ;1/128
.echo "Size: ",$-$9D95," bytes"
It is 386 bytes and I think it's reasonably fast for using floating point operations instead of integer or fixed-point arithmetic.
I also made a stand-alone
Mandelbrot Set Explorer a few years ago, which I think is a lot cooler, but is 1647 bytes and you can't achieve as much of a zoom (this float-based program allows about 500x greater zoom). Then again, the explorer allows you to navigate the Mandelbrot set, zoom in and out, and change how many iterations are used, while the Floatlib one just draws a fixed image (though you can change the source and recompile).
