The cassette port on the Coco used two audio tones to represent binary
data, 1200 HZ (1) and 2400Hz (0). Each tone ran for some number of mS
(I can't remember what the duration of the tones was). This was so that
the cassettes could be duplicated on an audio tape duplicator and for
noise immunity.
The tape hardware/software had 3 bits, 1 for reading data, one for
writing data and one to start and stop the tape. A simple RC circuit
provided additional noise immunity. The software had to measure the the
duration of the square wave for reading and make the square wave for
writing.
On 1/30/2023 11:14 AM, Chris via cctalk wrote:
It had a dedicated cassette port? Don't most cassette ports resemble a serial
port, or is my wonky brain making that up? What protocols did most cassette
ports use (c64/128?, IBM 5150, coco ...)?
