YUV input for LCD screens

[Stilton]

I have a PAL SC3000h computer and want to get component (RGB or YUV) out of it. People have done this with MSXes which have the same VDP (TMS9929); though it takes building a circuit to convert the chip's luminance and color difference to RGB. I was thinking it would be nice to bypass using that circuit  and get a cool 8-bit laptop in the deal if I could find an LCD screen that takes YUV, YCrCb, YPrPb, or whatever they're calling it on Mondays.  Is there such a beast? All the mobile LCD screens I've found take composite (except one which takes s-video).

Thanks in advance for any help!
Stilton

[benzaldehyde]

If it's a computer, then it should do RGB, which is distinct from component (YCbCr). I've heard that Sony PS1 LCD screens work marvelously (sp?), and do accept RGB input. As I'm from the wrong side of the ocean ( ), I'm not sure if there are PAL versions of the display.

[Stilton]

I had been thinking of PS One screens, but I am more interested in not having to build a circuit at all. If I am limited to an RGB display, then I will concentrate my efforts on building the circuit, though, and hook the thing up to my XRGB.

The SC3000 is a computer, yes, but from way, wayyyy back: 1983. I don't think RGB was standard back then (the standard output is composite, which, granted, is a lot better than the usual RF). This is the best info I could find about the pinouts of the chip:

      +----+--+----+
 RAS* |1 o       40| XTAL2
 CAS* |2         39| XTAL1
  AD7 |3    T    38| CPUCLK        R-Y  on TMS9928A/TMS9929A
  AD6 |4    M    37| GROMCLK
  AD5 |5    S    36| COMVID        Y    on TMS9928A/TMS9929A
  AD4 |6         35| EXTVDP        B-Y  on TMS9928A/TMS9929A
  AD3 |7    9    34| RESET*/SYNC
  AD2 |8    9    33| Vcc
  AD1 |9    1    32| RD0
  AD0 |10   8    31| RD1
 R/W* |11   A    30| RD2
  Vss |12        29| RD3
 MODE |13        28| RD4
 CSW* |14        27| RD5
 CSR* |15        26| RD6
 INT* |16        25| RD7
  CD7 |17        24| CD0
  CD6 |18        23| CD1
  CD5 |19        22| CD2
  CD4 |20        21| CD3
      +------------+

I have a pdf of the relevant circuit to get RGB and sync out of pins 35, 36, and 38.  But if there seems to be a more direct way to get RGB out of this mess, then I would love to know (I hate to solder!).

[benzaldehyde]

Whoa. Back in 1983, I didn't think that component video existed! RGB has been the standard for a good long time (i.e. so long as we've had color displays). RGB is actually better than component video; the former is usually the rawest form of video direct from yon video processor. Component is encoded, though the difference between picture quality from RGB to component is academic; it depends more on the quality of your display. It does indeed look like you're getting component video out of a 21 year-old machine. I'm not sure what to say, other than using that circuit to get the RGB out. Soldering isn't that bad, after the first few burns heal . As an aside, though, I'd love to see that transcoder circuit of which you are speaking. Is there a source from which you can trace the composite video line? That would require an encoder (possibly on another IC), which might also have a transcoder function.

[Stilton]

Sega was always fairly far-thinking in design, if not business practice. I've actually been using my Mega Drive/Genesis model 1 composite video cable with the SC3000, since I just got the bare system. But I probably would have been able to use the SC3000 cable on my Genesis just as easily.

Anyway, the schematic is right here: http://www.funet.fi/pub/msx/programming/tx...elf/rgbmsx1.pdf

It's also in Dutch, which doesn't add to my confidence in building it. Ah well, at least there're SI units to help me out.

The circuit doesn't seem to connect to the composite video pin (composite sync is connected with luminance, I think).

Stilton

[benzaldehyde]

Wow. I think you've just inadvertently contributed the first component to RGB transcoder circuit diagram I have ever seen on the Internet. It isn't even terribly complicated! Yes, luminance carries the sync signal, as does composite video. What a pain, though. I assume because you live in a PAL country RGB is a little more prevalent. Looks like the circuit might be your best option. You could also invest in a ready-made transcoder, like the XSelcect-D4. It's pricey, but there have been good impressions posted in the forum about it.