tixy.boot by Rick Companje, 2021-2022, MIT licence. 512 bytes bootsector code for 8086
A tribute to Martin Kleppe's beautiful https://tixy.land as well as a tribute to the Sanyo MBC-550/555 PC (1984) which forced me to be creative with code since 1994.
The Sanyo MBC-55x has a very limited ROM BIOS. After some hardware setup by the ROM BIOS a RAM BIOS loaded from floppy takes over. This means that we don't have any BIOS functions when running our own code from the bootsector.
The Sanyo has no display mode 13 (not even with the original RAM BIOS). It uses a 6845 video chip with three bitmapped graphics planes and is organized as 50 rows by 72 (or 80) columns. One column consists of 4 bytes. Then the next column starts. After 72 columns a new row starts. A bitmap of 16x8 pixels is made up of 2 columns on row 1 and 2 columns on row 2.
To run this code write the compiled code to the bootsector of a Sanyo MBC-55x floppy or use an emulator like the one written in Processing/Java in this repo.
t = time 0..255
i = index 0..255
x = x-pos 0..15
y = y-pos 0..15
result:
al -15..15 (size and color)
al<0 red, al>0 white
Note: this code is written for a Sanyo MBC-550/555 PC!
See tixyboot.asm for the full source code.
; ...
; using dx and bx registers as t,i,x,y variables
%define t dh
%define i dl
%define x bh
%define y bl
jmp setup
fx_table: ; the 'effects' table: 8 bytes, overwriting the 'Sanyo1.2' tag
db fx0,fx1,fx2,fx3,fx4,fx5,fx6,fx7
; ...
fx0: ; x
mov al,x
ret
fx1: ; y-7
mov al,y
sub al,7
ret
fx2: ; y+t
mov al,y
add al,t
ret
fx3: ; y-t
mov al,y
sub al,x
ret
fx4: ; sin(x+y+t)
mov al,x
add al,y
add al,t
call sin
ret
fx5: ; bitmap_data[i+t]
push bx
mov al,i
add al,t
mov bx,bitmap_data
xlat
pop bx
ret
fx6: ; -8*(y-x)+t
mov cl,-8
mov al,y
sub al,x
mul cl
call limit
add al,t
ret
fx7: ; sin(sqrt(x^2+y^2))-t)
mov al,i ; isqrt_table[i] = sqrt(x^2+y^2)
push bx
mov bx,isqrt_table
xlat
pop bx
sub al,t
call sin
ret
; ...
setup:
; ...
draw:
; ...See tixyboot.asm for the full source code.