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cassette tape interface, terminal, etc.

I haven't quite given up on building the Z80 computer described by Ciarcia in his book, "Build your own Z80 computer". On the other hand, there are lots of details I still need to understand and also lots of things have changed since he wrote the book. One thing I'm hoping has changed is cassette players. The old one I have can't be started or stopped or controlled other than by pressing the mechanical buttons, which probably work through levers. So I don't hold out much hope for being able to modify it so that it will start, stop, play or record or change its volume level under computer control. (If I'm wrong about that, I'd like to know how to do it.) The alternative is to obtain a cassette player that can be controlled by electrical signals instead of push buttons, but I don't know how expensive they are or where one gets them, maybe used. If it isn't dirt cheap, it isn't worth it. (I've heard of e-bay but I'm not ready for that.)

Another peripheral that Ciarcia talks about is a CRT terminal. After reading what he has to say, I eventually realized that he was not explaining how to build a terminal, only how to build an interface from it to the computer he wants you to build. Terminals have changed a lot and the ones he had in mind have probably gone the way of the dodo. I recall that old computers, such as the Timex-Sinclair, had a TV interface which let you use your TV for a terminal using a game adaptor. Ciarcia doesn't seem to explain how to do that. But maybe TV's have changed so much that one can't do it that way either.

One can still get Z80 chips, so I guess my questions, stated and unstated, might boil down to this: how would one update Ciarcia's book so as to make home made peripherals with ingredients that are available today?

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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Reply to
Allan Adler
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The computer's design probably includes a relay to switch the cassette motor on and off: if so, you just need to find the player's motor lead, break it and install a connector of some sort and a matching plug from the relay contacts. As for the CRT terminal, a PC running any terminal emulator (Hyperterminal, TeraTerm etc.) will do the job. Wade Hassler

Reply to
Wade Hassler

You do realize that most cassette-based computers had extremely rudimentary file capability. It was not a particular burden to press the buttons on the cassette recorder. You wouldn't be doing it that often, and virtually none of the computers had the software to seek out a given file, or do rewinds, or whatever. You would not be sorting or filtering files back to tape, merely loading and saving results of a program or saving and loading a whole program.

You'd take that portable cassette recorder that you had sitting in the closet, and hook up the audio lines to your computer. If there was a volume control on the thing, you'd do some testing until until you got the levels right, and then you wouldn't have to fiddle with anything on an ongoing basis.

Many/most cassette interfaces had a separate line for controlling the motor on the cassette deck. You'd plug it into the then-common "remote" jack on the recorder, which existed precisely so you could start and stop the tape movement. So you could position the cassette to the point you want it, press the "play" and "record" buttons, but the tape isn't advancing until the relay kicks over.

You'd get short tapes, like ten minutes long, or use regular length and just save one file per tape. That way you didn't have to deal with fastforwarding and finding a specific file.

One in a while, someone would come up with a very fancy tape operating system, and they did require a fancier tape deck, but those were rare.

If you're still not convinced, then the fussier would find the innards from fancier tape decks. Raw transports intended for use in computer equipment, which were electronically controlled. They'd find them in the surplus stores, and put them to use.

I also have a recollection of one NEC tape deck intended for personal computer use that was electronically controlled; at least my recollection is that the buttons were not mechanically linked to the transport.

If you want a fancy tape deck today, then go to garage sales and rummage sales until you find a full blown audio tape deck that does have electronic buttons, and then start modifying it until you can control it remotely. But realistically, you won't need it.

You might want to give consideration to moving to a floppy drive. Those were rare back then, but one company put out a hybrid. They used the drive much like a cassette recorder, and did not bother with much of an operating system. You'd tell the program where on the floppy you wanted to save it, and write that down on paper. There was no directory on the floppy, and you were dealing in terms of sector and track number, much in the way you'd write down the tape counter on the cassette deck. By moving to floppy, you'd get your remote capability, and faster save and loading of files, but without the finicky-ness of the of the cassette, and without the trouble of a full blown operating system to deal with the floppy.

You have the advantage that you can pull computers out of the garbage that will be far better terminals than the "dumb" terminals of the era. All you have to do is run a terminal emulator program on that computer, and connect it to your Z80 computer over the serial interface.

Back then, terminals tended to be costly, and you'd either scrounge up something at a surplus store, or build your own termial. Yes, you'd often hook that up to a TV set (they were more available and cheaper than monitors), but those terminals tended to be very rudimentary and only able to display a handful of characters on the screen. Once you got fancy, you were dealing with building a whole separate computer.

Hence, what you'd usually see is a video board, just like you'd plug into your computer today though not as fancy, so the CPU in the computer could function as the controller for the video section. But not only did you have to build the circuit, but you'd have to figure out the software (difficult if you don't have a working computer), and the video board likely would use up memory space in the computer.

Michael

Reply to
Michael Black

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