Spinning off from the momentum of my JX-3P decoder, I’m attacking the TI tape decoder project again. Managed to successfully detect the tape dumps and get a bit stream, overcoming all the problems of the first attempt. But decoding the bitstream into program code is going to be harder than I thought.

I was hoping that the TI-BASIC program would be stored on tape as the raw source code text. That’s not the case. The only readable bits in the bitstream are the strings from all the PRINT, REM, and CALL commands. Everything else appears to be packed into middle-level code; TI-BASIC is doubly-interpreted from source text to a secondary code which is then interpreted by the TI monitor program. So it’s just as I feared.

If I’m to make progress, I have to figure out how the variables, line numbers, commands, and their arguments are packed into symbols and delineated in the bitstream. Good luck on that without some outside help and lots of time at a hex editor.

Published by Shawn

He's just this guy, you know?