Search found 110 matches

by zx80nut
Thu Mar 07, 2013 8:19 pm
Forum: Sinclair Misc
Topic: Jupiter Ace redrawn (next step from the ZX80?)
Replies: 18
Views: 7860

Jupiter Ace redrawn (next step from the ZX80?)

I know not "strictly" Sinclair, but is a development team offshoot from what I remember, so I hope you don't mind me posting this, but "I've been at it again" (or, as my wife would put it, "got too much spare time.") Just as I did for the ZX80, I've been doing for the Jupiter Ace (those who know me ...
by zx80nut
Mon Nov 05, 2012 1:28 pm
Forum: Hardware
Topic: Are there any ZX80/81 Gerber PCB files available?
Replies: 6
Views: 3643

Re: Are there any ZX80/81 Gerber PCB files available?

I've done a little search and apparently there are bitmap to gerber converters available. No idea how good they are, but you could use them. ...Googling should give you what you want. The images are in PDF as they can be secured as a complete package and I don't want them spread about with no refere...
by zx80nut
Mon Nov 05, 2012 12:47 pm
Forum: Hardware
Topic: Are there any ZX80/81 Gerber PCB files available?
Replies: 6
Views: 3643

Re: Are there any ZX80/81 Gerber PCB files available?

Hi. The latest files (in the zip) on my website contain drill/throughhole cooordinates, but the design is not in a gerber format as the intention was to produce a graphically "precise" PCB layout, and this has been produced at 600dpi, which is more accurate than would be needed for photo etching. ht...
by zx80nut
Thu Oct 25, 2012 5:24 pm
Forum: Development
Topic: Houston, we have an image!
Replies: 135
Views: 82942

Re: Houston, we have an image!

You only assume that the discrete logic of the ZX80 has been packed into the ULA without any modifications. I don't assume that at all ! But as they had a working design, then why bother trying to alter much of it with very short timescales? We could go on forever on this, but I maintain that it is...
by zx80nut
Thu Oct 25, 2012 1:13 am
Forum: Development
Topic: Houston, we have an image!
Replies: 135
Views: 82942

Re: Houston, we have an image!

Hmmm... I can see no point in delaying by half a clock - that is additional logic which in this case would be wasted. Why would they bother with the extension to the ROM CS if they already had the data in the buffer? As I said, I cannot see the extension to the CS being accidental, as it fits perfec...
by zx80nut
Wed Oct 24, 2012 11:05 pm
Forum: Development
Topic: Houston, we have an image!
Replies: 135
Views: 82942

Re: Houston, we have an image!

Although the actual load point has not been proven yet, the scope pics of the ZX80 and ZX81 reveal that the character appears exactly the same time very shortly after the T1 rise of the next opcode. As the ZX80 loads the character shift reg at the start of the T1 period and the two machines are prod...
by zx80nut
Tue Oct 23, 2012 3:19 pm
Forum: Development
Topic: Houston, we have an image!
Replies: 135
Views: 82942

Re: Houston, we have an image!

Yes, but in that case, Wilf is not correct.
To implement exactly as a ZX81, it needs extending. As you have designed the ULA logic yourself, it doesn't need it.

Grant
by zx80nut
Sun Oct 21, 2012 11:49 pm
Forum: Development
Topic: Houston, we have an image!
Replies: 135
Views: 82942

Re: Houston, we have an image!

As Wilf Rigter writes in his ZX81 Video Tutorial, the ULA reads data into the shift register with falling edge of T4. So normal enabling RAM through /MREQ is sufficient without any floating datalines. That's why I asked for what a stretched /ROMCS would be good. Careful ! That's what Wilf's design ...
by zx80nut
Thu Jul 19, 2012 12:08 pm
Forum: Hardware
Topic: ZX80 is producing inverted characters..
Replies: 11
Views: 15765

Re: ZX80 is producing inverted characters..

Hee hee - I stared at the original post for ages trying to see what you were on about, then I saw it :)
by zx80nut
Thu Jul 19, 2012 10:56 am
Forum: Hardware
Topic: My new ZX80 built using my foil replicas
Replies: 10
Views: 12318

Re: My new ZX80 built using my foil replicas

Thanks for the info. You are correct about not needing a ZIP, but I put it in there so that the ZIP acts as a package so I can change the contents but keep the file link the same. In there was PCB Foils 1.8.pdf - I have now also added in there the drill coordinates :) The contents of the drill text ...