ZX81 I/O interface for your projects

Discussions about Sinclair ZX80 and ZX81 Hardware
sirmorris
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Joined: Thu May 08, 2008 5:45 pm

Re: ZX81 I/O interface for your projects

Post by sirmorris » Tue Jun 09, 2015 11:52 am

Make sure you keep us informed of your progress :D It will be fun!

Rishi
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Joined: Mon Jun 08, 2015 6:57 pm
Location: Amsterdam

Re: ZX81 I/O interface for your projects

Post by Rishi » Wed Jun 24, 2015 11:40 am

So i got mine to work as well ! finally after all these years. :D
The printplate wasn't to good anymore, actually i think it wasn't ever to good to begin with. inefficient in it's layout and not the best quality, still if soldered once correctly it should be fine. I still have to add the transistor to RAMCS, but without it it works just fine as well, although i'm not sure what happens if you use 16K Ram.
32K SRAM WRX compatible, 32Bit IO-Port, ROM Ghost, ZX-Printer.

Rishi
Posts: 107
Joined: Mon Jun 08, 2015 6:57 pm
Location: Amsterdam

Re: ZX81 I/O interface for your projects

Post by Rishi » Wed Jun 24, 2015 10:17 pm

Actually i started thinking about the RAMCS connection but then realized that it no effect once you plug in the 16K RAM extension, since then RAMCS is anyway high to disable the internal RAM, what should be done is disconnect MEMRQ to the back edge of the interface, and use a 7408 for that for instance. Anyway since it works as is i guess the whole thing is redundant although since i'm planning to build a 16-bit version i now plan to put that on the same print as the memory extension. (that should have emergency power i guess)
32K SRAM WRX compatible, 32Bit IO-Port, ROM Ghost, ZX-Printer.

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stefano
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Re: ZX81 I/O interface for your projects

Post by stefano » Thu Jun 25, 2015 8:42 am

I propably told about this already:
http://www.microatena.it/scheda_libro.php?id=198&ord=N

On page 78 (it's page #88 on the PDF scan) there's an output-only very compact circuit reacting to pokes in the range 8192..16383.
That crazy guy suggested to ..SOLDER it over the Z80 CPU !!

My variant I used on a Spectrum had a less invasive EDGE connector. I used it a lot to drive 8 220 volt lights with TRIACs .. the Spectrum permits to write your own IM2 mode interrupt driver so the software could stay in sync with the lamps alternate current and avoid beating.
It was very good, actually, but it is difficult to show it.. the emulated version does not help either. But... wait ! could such "interface emulator" help you if we hook it to the EightyOne emulator ?

viewtopic.php?f=14&t=1486#p15607

Rishi
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Location: Amsterdam

Re: ZX81 I/O interface for your projects

Post by Rishi » Thu Jun 25, 2015 8:56 pm

i don't know about the emulators, ehm few things, - this is output only. that is a pity, - it seems to check if either pin A15 || A14 ||A13 is being written to, so if the address is below 16384, it is not a bad idea to use lower addresses but how would that work for input ? using a 74ls373 instead of the 74ls273 seems overkill, since this is the output bus :D the third state has no purpose, but works just as well. If i'm only using on/off i think i would use relays.
32K SRAM WRX compatible, 32Bit IO-Port, ROM Ghost, ZX-Printer.

geheniau
Posts: 1
Joined: Thu Feb 08, 2018 8:03 pm

Re: ZX81 I/O interface for your projects

Post by geheniau » Thu Feb 08, 2018 8:07 pm

Well, I build my own interface from this book with 220v Light Bulbs in 1984.
I found the program on cassette and have rebuild it this month!
Thanks for PCB made it again with Adobe and a Chinese PCB maker.
If you have questions or like it, let me know via PM


IT STILL WORKS:

https://www.youtube.com/watch?v=BznpFw5 ... e=youtu.be

https://youtu.be/BznpFw5QmmU
Last edited by RWAP on Thu Feb 08, 2018 8:47 pm, edited 1 time in total.
Reason: Removed direct email address in the post to prevent spam!

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1024MAK
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Location: Looking forward to summer in Somerset, UK...

Re: ZX81 I/O interface for your projects

Post by 1024MAK » Fri Feb 09, 2018 1:11 am

Nice :D

Mark

sirmorris
Posts: 2813
Joined: Thu May 08, 2008 5:45 pm

Re: ZX81 I/O interface for your projects

Post by sirmorris » Fri Feb 09, 2018 9:52 am

Superblinkenlights! Nice work :D

dessony
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Location: Indiana, USA

Re: ZX81 I/O interface for your projects

Post by dessony » Sun Feb 11, 2018 12:53 pm

Real Awesome! :-D :lol:

rom475
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Joined: Wed Jan 17, 2018 10:26 pm

Re: ZX81 I/O interface for your projects

Post by rom475 » Fri Apr 06, 2018 9:29 pm

Definitely a very nice I/O Board...I do ask tho' would this be for a single peripheral board to control
such as a AY3-8910,12,SPO256A-AL2 addon? I ask because I saw that has no expansion device select coding
for multiple add ons?

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