Re: A cheap, easy PC to apple transfer idea

[Rubywand <rubywand@swbell.net>]

Bob Keyes writes ...
> 
> Nathan Mates wrote:
> >
> > .... Serial ports are very much optional equipment that not
> > everyone has, especially early //es and ][/][+s. If you've got a GS,
> > great. However, plenty of people don't.
> >
> 
> Exactly, hence the idea I had. Since no one has volunteered to write the
> program, I will try to do it myself. Anyone have the specs on the apple
> tape interface? If not, I can try to dig them up out of old manuals, or
> figure it out with an oscilloscope.
> 
> After that, I need to get a book on sound-card programming.


     The Apple II tape interface runs at about 1330 baud (average). It 
uses pulse width differences to identify 1's and 0's. This scheme is kind 
of odd since a pure zero-crossing detection approach is easier, more 
reliable, and produces higher baud rates. (Around 1800 baud seems to be 
the limit for normal cassette tape on cheapo portable rec/play units.)

     The Apple tape R/W code is annotated in the ROM listing presented in 
the Apple Reference Manual. (See page 165.)  Since you are not 
writing/reading tape, you can get higher baud rates using the Apple II 
scheme by going to shorter pulse widths.


Rubywand