On Mon, 11 Oct 1999, Martijn van Buul wrote: > It might be worthwhile to contact Markus Brenner then -- He wrote > this tap2voc program, and can doubtlessly tell us how the **** that > tape format works. Indeed a good idea. BTW, when I met Daniel Dallmann last Sunday in Frankfurt, we discussed this tape thing a little. It occurred to me that there's absolutely no need for that GCR coding. On the floppy drive it is required, because the bit rate may vary. On the CD it is constant. Therefore, we can use 8 samples for data and 1 or 2 samples for "stop bits", to allow for storing the byte and for resynchronization. The raw speed would still be 4410 or even 4900 bytes per second, although I think that the latter (doing only with one stop bit) would require scattering the pointer incrementation and comparison operations in the unrolled byte-receive loop, which is a somewhat non-trivial task. Had these conferences I'm participating in been more boring, I'd probably already have such a routine. :-) A word on the hardware. I think it could be done with 3 or 2 ICs. One amplifier-limiter (for converting the line-level signal, 1 volt peak-to-peak or something like that, to TTL, maybe with some sort of a Schmitt trigger), and something to convert the rising and falling edges of the signal to pulses between 1 and 21 microseconds (those are the limits for the pulse width; the actual width should be constant). Maybe you can combine these two steps. Power is available from the cassette connector. Marko - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail email@example.com.
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