Tape Interface

What have you built or do you want to design to go with your replica 1

Tape Interface

Postby Davie Byrne » Jan Mon 16, 2006 10:52 am

I was wondering what were the problems with the tape interface? I might have a friend who could help out.
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Postby vbriel » Jan Tue 17, 2006 8:29 am

Haven't been able to get the interface to read back from tape. I built a board from the original schematics that recorded to tape just fine won't read the data back from tape.
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Postby randy » Jan Tue 17, 2006 8:48 pm

I've been looking into making one but not had much time to study it.

How does it work?
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Postby vbriel » Jan Wed 18, 2006 5:02 pm

There are schematics out there for it, but it has an error. Actually I believe the Apple 1 had error on the schematic IIRC. If you can't find, I'll post it on my site.

The cassette interface works but pumping out the memory from a range entered. It gets set to a specific memory location that converts the bytes into an analog signal via a simple 3 resitor D/A circuit. The issue is with reading the analog signal back. The apple 1 cassette interface used a LM311 voltage comparator to read the analog signals in and convert them back to digital bytes. I have the code for the cassette interface, I even built a slightly modified circuit only changing the type of rom used and can't get it to read back from tape. Nothing. The 311 reads bits based on a voltage swing from +5V to -5V. Everytime the signal crosses the 0V range it counts a bit. Timing is everything and thus far, it isn't working. Hopefully I can find time to work on it again soon.

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Postby randy » Jan Mon 30, 2006 9:48 pm

Thanks for the info. I did find the schematic.

Could you describe how your video section works?
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