Re: cassette interface data format?

[...]

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

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