Basically the TI selection screen doesn't scan ROM banks anymore.
From the TI-INTERN book;
01FD : CEQ @>6000,>AA ROM Header? OH!!! / Not at GROM V2.2 0202 : BR GROM@>0224 / 0204 : DST @>8358,@>6006 Next program start / The other shifted 0209 : DCZ @>8358 / accordingly 020B : BS GROM@>0224 / 020D : INCT @>8372 / 020F : DST *>8372,>FFFF Flag on stack / This change eliminates 0214 : INCT @>8372 / the ROM moduls 0216 : DST *>8372,@>8358 Address on stack / 021A : INC @>836C 2nd program? / 021C : DST @>8358,@>0000(@>8358) / 0222 : BR GROM@>0209 /
So I'm trying to find a way how to start my game on an (unexpanded) V2.2 TI-99/4A anyway.
These are the options I'm thinking about
1) Bypass the TI-Title screen and start the game right away. There are couple of game modules out there that do that.
I think the Milton-Bradley games do that.
Is that possible without adding any extra hardware to the cartridge ?
Does the DSR scan routine also check the cartridge space. Would that help?
2) Add a "CALL GAME" command to TI-Basic that branches to the game in the cartridge space.
Don't think that's possible without GROM on the cartridge. If we have GROM, then the game is scanned anyway.
EDIT: How do they do it with Munchman and TI-Invaders? These are ROM only games, and I suppose they work on v2.2 consoles.
Probably some extra chip on the cartridge ?
3) Write a fake VDP header on cassette tape to fool the GPL interpreter and start the game.
You basically have the cartridge and a cassette tape. You load from the cassette tape to trigger the cartridge.
No, that's not an option
Any ideas ?