Re: cassette interface data format?

["Jayson Smith" <nospamratguyspambegone@nospamplease.bellsouth.ihatespam.net>]

There is no lead tone at the end.  You can see that if you've ever listened
to a valid cassette dump.
Jayson.

"Benjamin Ketcham" <bketcham@drizzle.com> wrote in message
news:1097295086.139412@yasure...
> Paul R. Santa-Maria <paulrsm@buckeye-express.com> wrote:
> >
> > The original Apple II system monitor listing is at
> > http://linux.cis.monroeccc.edu/~paulrsm/6502/
>
> Ah, thank you very much for this info.  Should be helpful...
>
> An update on the project so far:
> Using the info below from Michael J. Mahon, everything seems correct
> except at the end, the post-data framing.  I get an "ERR" -- but
> all the data is transferred correctly.  It's as if my checksum
> is wrong, or as if some other signals or codes are expected in
> addition.  I tried sending another "start" code, or going back
> to the "lead in tone", but makes no visible difference, still
> get "ERR".
> Hopefully I can reverse-engineer what is expected by looking
> at the ROM listing (I have a ][+, but AIUI the cassette data
> format is unchanged since the Apple I).
> I appreciate everyone's help.
>
> --Benjamin
>
> ----
> From mjmahon@aol.com Fri Oct  8 20:59:48 2004
> Newsgroups: comp.sys.apple2
> Date: 06 Oct 2004 07:57:30 GMT
> Subject: Re: cassette interface data format?
> Message-ID: <20041006035730.10671.00002072@mb-m04.aol.com>
>
> [...]
>
> The best "documentation" of cassette format is in the monitor
> listing for the code that creates and decodes cassettes.  The
> listing is in virtually all early Apple II Reference Manuals.
>
> There is a lead-in tone of 3.5 seconds of 770Hz, followed by
> a 1-cycle "start" mark with two 400 microsecond half-periods.
> Then data follows, most significant bit first, with two 250
> microsecond half-periods for a "0" and two 500 microsecond
> half-periods for a "1".  Following the data, there is a single
> checksum byte, which is the EOR of all data bytes, seeded
> with $FF.
>
> Applesoft BASIC files are preceded by a short record with
> the length of the program and an "auto run" flag byte.
>
> -michael
>
> Check out parallel computing for 8-bit Apples on my
> Home page:  http://members.aol.com/MJMahon/
>
>