ZX81 ULA-in-a-CPLD

Any discussions related to the creation of new hardware or software for the ZX80 or ZX81
McKlaud
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Re: ZX81 ULA-in-a-CPLD

Post by McKlaud » Mon Apr 30, 2018 6:06 am

:D Andy, nice features :D
Claudius
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Andy Rea
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Re: ZX81 ULA-in-a-CPLD

Post by Andy Rea » Wed May 16, 2018 9:46 pm

little update second prototype PCB arrived and i have built one up, a little tweaking with the tape inout circuit and all is well.
top side:
Image
bottom side ( still ocvered in flux :o )
Image

tape input works reliably with my Timex branded cassette player i can load programs with volume between 5 and 7... with a " perfect source " OTLA found here https://code.google.com/archive/p/otla/ i can load 3D monster maze in as little as 9 seconds, with windows volume anywhere from 50% to 90% OTLA works surprisingly well.

The 2 other proto boards will be built ( and cleaned ) in the next few days and after testing, a couple of lucky forum members will be gifted these boards for further testing / evaluation / end user experience blah blah....

If all goes well i will order a larger quantity of boards and get building.

Regards andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

Lardo Boffin
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Re: ZX81 ULA-in-a-CPLD

Post by Lardo Boffin » Wed May 16, 2018 9:51 pm

Andy Rea wrote:
Wed May 16, 2018 9:46 pm

If all goes well i will order a larger quantity of boards and get building.

Regards andy
:o :shock: 8-) :D

I couldn’t see an ‘excited’ smiley.
ZX81 iss 1 (bugged ROM, kludge fix, normal, kit)
Iss 3 with ZXVid, another in nearly perfect box
TS 1000 iss 3, ZXPand AY, ZX8-CCB & ZX-KDLX
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Spectrum 48k
Toastrack + DIVMMC future

McKlaud
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Location: St Albans, UK

Re: ZX81 ULA-in-a-CPLD

Post by McKlaud » Wed May 16, 2018 10:04 pm

I am impressed with your progress, Andy. Well done and the board looks stunning. :geek: :geek:
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1024MAK
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Re: ZX81 ULA-in-a-CPLD

Post by 1024MAK » Wed May 16, 2018 10:26 pm

IMG_7073.JPG
IMG_7073.JPG (26.73 KiB) Viewed 138 times
He drooled uncontrolledly as he typed the message...

Lovely work there, well done Andy 8-) :D

Mark

Moggy
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Re: ZX81 ULA-in-a-CPLD

Post by Moggy » Thu May 17, 2018 11:34 am

Looks good,Andy and it also means longevity for our zeddies as it will replace this most important yet obsolete component. :ugeek:

nollkolltroll
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Re: ZX81 ULA-in-a-CPLD

Post by nollkolltroll » Thu May 17, 2018 1:17 pm

Very nice to have some proper replacement for our aging HW.
Any plans for further functions, like a super ULA?
/Adam

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TMAOne
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Re: ZX81 ULA-in-a-CPLD

Post by TMAOne » Thu May 17, 2018 9:13 pm

Congratulations Andy!

This is truly a milestone in Zeddy history, as I know many otherwise good examples have gone to the dumpster for lack of a replacement ULA.

Good going. I look forward to them being widely available.

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Andy Rea
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Re: ZX81 ULA-in-a-CPLD

Post by Andy Rea » Thu May 17, 2018 10:00 pm

built the other 2 this evening and after testing both worked as expected, i then tried one inside a real zx81 case... oh my :geek: the link in the middle is mighty close to touching the case ... the easiest thing would be to fit a right angle header. (might have to bend it up slightly :? ) the link is there to add a 75 ohm load should you be unlucky :lol: enough to own a monitor / tv that has a high impedance input.....

On second thoughts looking at the picture again i could just lose the plastic bit on the bottom of the pins so when fitted the shorting link would sit on the PCB. that would easily provide more than enough clearance.

Image

isnt it funny how the colour of the caps change with the angle... c1, c5, c6 ,c9 are all the same ( from the same strip )

Image

the eagle eyed may notice that pin 36 does not have a SIL pin in it, this is now an input that can be left unconnected for standard operation or grounded to enable M1NOT operation.

so erm yeah.... thats it for now....
nollkolltroll wrote:
Thu May 17, 2018 1:17 pm
Very nice to have some proper replacement for our aging HW.
Any plans for further functions, like a super ULA?
Not at this time other than M1NOT and that happened as an afterthought and then only because i am using on board oscillator so have a pin free.

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

McKlaud
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Re: ZX81 ULA-in-a-CPLD

Post by McKlaud » Thu May 17, 2018 10:54 pm

Image
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