Welcome, Guest. Please login or register.


Author Topic: External colour input (Read 5926 times)

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13706
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: External colour input
« Reply #15 on: 2016.December.03. 23:55:35 »
In 256 color I think about two cases: it is select from the first 16 colors, or it is don't used.
Interesting question what happen in attribute mode? It is replace the attribute byte?
And in hw character mode? Select the ink colour? Or paper color? Or both? :-)

And also interesting what happen if the external colors using better resolution? For example 640 pixels, in 4 colors 320 pixels Nick mode. It is keep the original wide pixels, or can make smaller pixels?

Offline lgb

  • EP addict
  • *
  • Posts: 3535
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://lgb.hu/
Re: External colour input
« Reply #16 on: 2016.December.04. 00:21:46 »
Surely, just guessing. Just it's 4 bits info, thus 16 colours, that mades me thinking it's similar to the 16 colour Nick "internal" mode. But I can be totally wrong :D Anyway, since it is designed for future sprite support there should be some "sane logic" how it should work, just needs to be figured out. For attribute mode: I would _guess_ (!!!!) that it does not matter. It may be implemented simply, that Nick generates its pixel whatever it is video and colour mode. And the external colour mode generated pixel just shown "above" (better say "instead") the Nick generated pixel, that is, simple "priority decoder" or something like that.

Btw! Just come into my mind: if I remember correctly, we have some kind of Nick internals document or something ... Hasn't that contain some information to answer these kind of questions?

Online gflorez

  • EP addict
  • *
  • Posts: 2867
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #17 on: 2016.December.04. 08:48:20 »
Yes, documents DPC11 and DPC12 have information about the internals of Nick, and we also have the schematics here and here, but very high technical knowledge is needed to understand them.  Surely Pear has it...

Offline pear

  • EP lover
  • *
  • Posts: 795
  • Country: pl
  • Z80 only
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #18 on: 2016.December.04. 09:58:56 »
Wow, finally some specifics :)
I had not thought before about TVC64. Only recently I learned about its history, and that is very similar to the Enterprise.
Something else is analyzing the schematics on the paper, and something totally different opportunity to see in the operation of the actual hardware, without fear that the feeler "will fall to the place in which can cause the most damage" (according to Murphy's Law).
Thank you very much for the links.
Could use even the contents of ROM-s. Please :)

Online gflorez

  • EP addict
  • *
  • Posts: 2867
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #19 on: 2016.December.04. 12:33:48 »
What Roms, for EP or for TVC?

There is disassembly for the two computers, with Hungarian commentaries:

EP 0 Segment.
EP 1 Segment.

TVC Rom.


Zozo keeps a lot of EP information on his Web page.

And there is the official TVC Page.


Offline lgb

  • EP addict
  • *
  • Posts: 3535
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://lgb.hu/
Re: External colour input
« Reply #20 on: 2016.December.04. 12:48:11 »
My idea was, that a sprite unit would work this way: it has two "data structures" for a sprite. First, there is the "shape information". That is, controls /EXTC, this is 1 bit info per sprite pixel. Can be also thought as the "alpha channel" in modern gfx things, just we have only on/off, no "semi-transparency" etc. And then there is 4 bits of colour info for the given pixel, which does not count at all if /EXTC is not (low) active. Now it's interesting that it _seems_ I was right, in the "palette-less" 256 colour mode, the external colour still uses the palette. That makes sense, as this external colour feature is created for "sprites" keeping in mind in the future, this it would be a bit odd, that sprites can have only fixed colours for the first 16 EP palette colours. And anyway, in 256 colour mode the palette by Nick internal pixel generation is not used, so it's kinda handy to use it for something at least :-D Surely, for a more simple sprite unit, some can say, that external colour value 0 means the transparency, then no need for shape/colour info, but only a simple logic, to drive /EXTC for low active if 4 bits of EC are all zero. This would mean - if I am correct - that 0 would mean transparent, 1-15 would select the corresponding internal Nick palette (8 LPB palette values + FIXBIAS for the second 8). Thus we lost one colour with this technique. The price for not having separated sprite "shape" and "colour" info in the external sprite unit ...

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13706
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: External colour input
« Reply #21 on: 2016.December.04. 14:37:55 »
Could use even the contents of ROM-s. Please :)
Which ROM-s?
TVC ROMs. Basic, DOS
TVC Spectrum emu ROM

Online gflorez

  • EP addict
  • *
  • Posts: 2867
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #22 on: 2016.December.04. 14:42:28 »
They mention a camera input. May be the easiest way to experiment is to try a video input, with some circuit slicing a synchronised composite signal into its 4 bit EP-colour components, with Extcol always active.

Offline pear

  • EP lover
  • *
  • Posts: 795
  • Country: pl
  • Z80 only
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #23 on: 2016.December.04. 15:07:29 »
Now I have already all. Thank you.
Evenings are long. Slowly I redraw TVC and try to build a clone.

Offline lgb

  • EP addict
  • *
  • Posts: 3535
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://lgb.hu/
Re: External colour input
« Reply #24 on: 2016.December.04. 18:55:32 »
They mention a camera input. May be the easiest way to experiment is to try a video input, with some circuit slicing a synchronised composite signal into its 4 bit EP-colour components, with Extcol always active.

Yes, I guess. That's about the same what I meant about having a "nice resolution 16 colour mode" generated externally on the external colour inputs. As far as I see then, on TVC this method was used by the hardware ZX Spectrum emulator as well, basically, what Zozo mentioned above? Ok, that's TVC and not EP, but I think the theory is the same, after all.

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13706
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://enterprise.iko.hu/
Re: External colour input
« Reply #25 on: 2016.December.04. 20:15:13 »
There is the interesting question: Nick is a custom chip, what the developers wanted it, putted in.
But at the TVC used a existing chip (6845). How adapted this special features? And fully adapted?

Offline lgb

  • EP addict
  • *
  • Posts: 3535
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://lgb.hu/
Re: External colour input
« Reply #26 on: 2016.December.04. 20:25:03 »
There is the interesting question: Nick is a custom chip, what the developers wanted it, putted in.
But at the TVC used a existing chip (6845). How adapted this special features? And fully adapted?

As far as I can see, TVC uses also a custom "logic", not "a single chip" though, as with EP/Nick. In TVC, the 6845 only generates memory addresses, sync pulses, and things like that, but the actual pixel creation, modes, memory reading, CPU/video bus "sharing", etc are not task of the CRTC at all (and it seems these are all implemented by discrete logic?). Maybe that was (the part) of TVC's problem for being too costly to manufacture: it basically uses "discrete logic" for the task, where this was built-in all in a custom chip in the EP (it's another question, that a relatively high-integration custom stuff is also costly ... some must find the balance ...).

Offline BruceTanner

  • EP lover
  • *
  • Posts: 509
  • Country: gb
  • OS:
  • Windows NT 6.3 Windows NT 6.3
  • Browser:
  • Chrome 54.0.2840.99 Chrome 54.0.2840.99
    • View Profile
Re: External colour input
« Reply #27 on: 2016.December.05. 00:23:15 »
...Maybe that was (the part) of TVC's problem for being too costly to manufacture: it basically uses "discrete logic" for the task, where this was built-in all in a custom chip in the EP (it's another question, that a relatively high-integration custom stuff is also costly ... some must find the balance ...).

The problem with custom chips at the time the TVC was designed was that "the west" was not allowed to export custom chip technology to a soviet-bloc country (regulations known as COCOM) - that is why the TVC could not use Nick & Dave (in case the Soviet Union used them in missiles! :lol: )  This was right at the end of the Soviet era (but we didn't know that was going to the the case at the time!) but I'm not sure exactly when things changed - obviously by the time all the EPs were sold to Hungary it was OK but this must have been right at the changeover point. Or maybe it was possible to export complete computers but not individual chips, I can't remember.

Offline lgb

  • EP addict
  • *
  • Posts: 3535
  • Country: hu
  • æðsta yfirmaður
  • OS:
  • Linux (Ubuntu) Linux (Ubuntu)
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
    • http://lgb.hu/
Re: External colour input
« Reply #28 on: 2016.December.05. 00:46:38 »
Interesting, but it sounds me funny, if TVC would use Dave/Nick, it would be exactly an EP128, and not a TVC :) Well, or maybe they would have manufactured EPs for real, just "made in Hungary" and that was not possible? Anyway, I see USSR launching missiles but programming LPBs first for Nick in them :D

Online gflorez

  • EP addict
  • *
  • Posts: 2867
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 50.0 Firefox 50.0
    • View Profile
Re: External colour input
« Reply #29 on: 2016.December.05. 09:04:05 »
The TVC Spectrum emulator schematics are very clear for my poor knowledge. Extc\ is always put to ground, and it seems that Col0 is used for transparency, leaving Col1-Col3 for the colour input.