Exatron Stringy Floppy and CAI/O Interface

ZX80 / ZX81 hardware and software offered for sale or swapping
torrid
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Location: North Carolina

Exatron Stringy Floppy and CAI/O Interface

Post by torrid »

It's been fun to pull out my old ZX81 and see that it still works, but I've decided I don't have the time to devote to doing anything with it.

I have a couple of pieces of hardware that might be of interest to those still working with Sinclairs. I have an Exatron "stringy floppy" drive and the CAI/O controller for it. I would be willing to ship them, free of charge, to anyone that is interested in them. Preferably someone in the continental US to keep shipping costs down. I would like to find the right person who really wants to use them, not just flip them on eBay.

The Exatron drive was a good alternative to cassette tapes 35 years ago. As for data storage today, it is probably mostly a curiosity. The tapes are quite old and are known to break. The one that contains my childhood programming is shot, though I was able to load some games from another tape. If you are looking for storage, I would look at something more modern like the ZXPand.

The CAI/O controller may be of more interest to current hobbyists. In addition to controlling the Exatron drive, it has serial and parallel ports built into it. I never used them myself, but it might be a good way to get your Sinclair to talk to the outside world.

If you think this hardware may be of interest to you, please send me a private message on this board.

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RWAP
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Re: Exatron Stringy Floppy and CAI/O Interface

Post by RWAP »

That looks really interesting - it would be good if someone could scan the manuals and maybe the PCB of the interface / dump the ROM - at least so that if anyone else has one which doesn't work, they would have a starting point against a known working unit to find any issues!
torrid
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Joined: Mon Jun 20, 2016 4:10 am
Location: North Carolina

Re: Exatron Stringy Floppy and CAI/O Interface

Post by torrid »

I'll try to scan the manuals and post them here in a few days. There are even schematics, though the one for the CAI/O board isn't very legible.

To operate the Exatron drive, I had to open up the CAI/O and install an EPROM chip into a socket. At 13 years old I was terrified of breaking something, but it appears to have worked.
RWAP
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Re: Exatron Stringy Floppy and CAI/O Interface

Post by RWAP »

Many thanks - that sort of reminds me, we could do with a ZX81 resource site somewhere where all this type of stuff could be uploaded!
torrid
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Joined: Mon Jun 20, 2016 4:10 am
Location: North Carolina

Re: Exatron Stringy Floppy and CAI/O Interface

Post by torrid »

It was great to talk to different folks and reminisce about playing with ZX81s. The CAI/O board and ESF are on their way to a new home in Texas (ironically where dug them out of my parents house at Christmas after 30 years). Thanks to everyone who was interested.
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gammaray
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Re: Exatron Stringy Floppy and CAI/O Interface

Post by gammaray »

This unit has option for 3 ROM's but seems normally has only the one ROM by default with the device sold with it.

1. CAI/ESF ROM
2.MODEM "ASCII" ROM FOR SERIAL COMMUNICATION
3. PRINTER DEVICE ROM

RUNNING THE FOLLOWING:
A. SERIAL
B. PARALLEL - STRINGY FLOPPY ET AL.
THERE IS A PINOUT FOR VARIOUS CA I/O DEVICES:
C. CA TAPE
D. CA PRINTER

Does anybody have the other ROM images or other hardware schematics (T-16?).
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
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gammaray
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Location: Texas

Re: Exatron Stringy Floppy and CAI/O Interface

Post by gammaray »

This is another site that has all types of resources and historical records.

http://www.zx81stuff.org.uk/index.html
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
torrid
Posts: 13
Joined: Mon Jun 20, 2016 4:10 am
Location: North Carolina

Re: Exatron Stringy Floppy and CAI/O Interface

Post by torrid »

Missing ROMs? Sorry about that. Like I said, I only used it for the ESF drive.

Looking through the schematic, the I/O board has an 8250 UART and an 8255 PPI on it. I think these were fairly standard parts for the time.

The parallel port was used for communicating with the ESF, but is not limited to that use. The ESF ROM contained code specifically for the operation of the drive. The parallel port will still works with or without it.

I'm not completely sure, but it looks like the serial ROM contained code for converting ZX81 characters to ASCII characters so you could use a modem. The UART has two functional serial ports even without the ROM.

Don't know much about the CA Printer and CA Tape. I'm guessing all of that is lost to history.

I bet the entire CAI/O board functionality could be easily replicated on an FPGA today.
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gammaray
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Re: Exatron Stringy Floppy and CAI/O Interface

Post by gammaray »

It is still wonderful since I only every used the Exatron. I bought 28 stringy floppies that have TRS-80 programs on them...

Wonder if any Tandy guy would want these downloaded before I format them? I'll have to inquire.

I also wonder how long any of the floppies will last having been kept in sleeves. Best preservation I could realistically hope for.

My Exatron was from a different vendor using a single purpose interface.

There are two Exatrons for sale now for only $500... Hmmm...

I have already spent enough! Those floppies were not cheap.
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
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