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Speccery / EP994A

My TI-99/4A clone, two versions: FPGA+TMS99105 CPU and FPGA with my CPU core
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[FR] External audio input for loading real tapes #7

Open lroby74 opened 4 years ago

lroby74 commented 4 years ago

Hello, would be possible to add real tapes loading via a tape recorder and using external audio jack input?

Thanks in advance

Best Regards Roberto from Italy

Speccery commented 4 years ago

Hi Roberto, Good request. Would be interesting to check it out. The timing would be the obvious challenge, I need to check how the original TI-99/4A handles tape loading. I seem to remember that it would be timed with the hardware timer built into the TMS9901. If that is true, then implementing the tape loading would be a lot more feasible. If the timing is based on software, it would be much harder as the CPU is running so much faster and with different timing.

lroby74 commented 4 years ago

Hello again, i've just discovered that all TI994A tape games are on WAV format, so would be enough to enable WAV reader from external audio input (IMHO!) to solve problem?

nippur72 commented 4 years ago

this page has some details on the cassette tape interface: http://www.unige.ch/medecine/nouspikel/ti99/cassette.htm

According to it, timings are done via the TMS9901, so in theory it's a matter of connecting the CRU bits 25 and 27 to the audio input and output bits. I guess the motor can be simply ignored.

Anyway when I do a SAVE CS1 (gyurco's fork for the Mist board) it gets stuck on the * RECORDING phase, never completing it. Perhaps there's something missing with the timings?