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I'm trying to make a home console port of Space Race using visual batari basic. (Its my first time coding a game). I'm coding my game. Everything is going fine, but when I compile and then attempt to test the game with Stella, an error message appears in Stella.


Fatal Error

Invalid Instruction.


So I tried it with Z26. But when I compile and open the game, instead of opening the game, it opens to a black screen with the word jammed at the bottom.

Please help me. I looked everywhere but I haven't found a way to fix this.

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I doubt it's the emulator. Sounds like the compiled code is hitting one of the 6502 JAM instructions which effectively kills the cpu from fetching new instructions. http://forum.6502.org/viewtopic.php?f=1&t=1409&view=previous


The only way to restore the cpu to a valid state once it's jammed on real hardware is sending a reset signal to the cpu. The error message you are seeing is alerting you to the fact the cpu has attempted to execute one of the JAM instructions and is now in an unresponsive state.


VICE actually has test programs to ensure once a JAM instruction is executed the cpu indeed remains frozen. These test programs show that jam instructions can be compiled with no issues. https://sourceforge.net/p/vice-emu/code/HEAD/tree/testprogs/CPU/cpujam/

Edited by willymanilly

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If you don’t want to post the code, you could always PM it to me and I could take a look and see if I notice anything that might be causing the problem. If I find something, I’ll add the error and the fix to the bB page.

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