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Here is a program that will scroll through the various graphics icons that are built into the Odyssey 2 system ROM:
cpu 8048
org 0400h
jmp 02C3h ;system start or reset - select game
jmp 0009h ;external IRQ - vblank routine
jmp timer ;timer IRQ
jmp 001Ah ;vblank service - vblank (collision and clock)
jmp start
jmp 0044h ;continuation of vblank service - vblank (tune)
timer retr ; we don't do anything with timer IRQs
start
call 011Ch
mov r2,#31h
inp call 013dh
mov a, r2 ; r5 is destructive on vid call
mov r5,a
inc r2
add a, #0c1h
jnc vid
mov r2,#31h
vid mov r0,#10h ; starting char in VDC
mov r3,#20h ; x-position
mov r4,#20h ; y-position
mov r6,#09h ; color
call 03eah ; display char
call 0127h ; start display
jmp inp
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The program starts with 31h, which, as you can see in this article, is a ball. C1h is added until there is a carry, which tests for the last graphics character of 3Fh by adding 31h to r2, which is copied to r5 for the dislay routine and is destructive to r5.
To assemble this program and run with o2em:
usr-1@wrk-1 kb $ asl k.asm
macro assembler 1.41r8
(i386-unknown-linux)
(C) 1992,1998 Alfred Arnold
Mitsubishi M16C-Generator also (C) 1999 RMS
TMS320C2x-Generator (C) 1994/96 Thomas Sailer
TMS320C5x-Generator (C) 1995/96 Thomas Sailer
assembling k.asm
PASS 1
k.asm(29)
PASS 2
k.asm(29)
0.03 seconds assembly time
29 lines source file
2 passes
0 errors
0 warnings
usr-1@wrk-1 kb $
usr-1@wrk-1 kb $ p2bin k.p k.bin -r \$0400-\$0bff -l 0
P2BIN/C V1.41r8
(C) 1992,1998 Alfred Arnold
k.p==>>k.bin (42 Byte)
usr-1@wrk-1 kb $
usr-1@wrk-1 kb $ o2em k.bin
O2EM v1.16 (Dec/2004) - Linux binary
Free Odyssey2 / Videopac+ Emulator - http://o2em.sourceforge.net
Developed by Andre de la Rocha
Created by Daniel Boris (c)1996/1998
Starting emulation ...
Initializing sound system...
Sound system initialized ok
Sound driver [Open Sound System] detected
Using Allegro Allegro 4.0.3, Unix
Odyssey2 bios ROM loaded
Loading: "k.bin" Size: 2K CRC: 2341BC85
Loading voice samples... 0 samples loaded
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Here is what the screen looks like:
Just press any key on the keyboard, and the character changes and makes a beep. It wouldn't take too much more to make this into a simple keyboard banger.
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