C128 on TV screen

[yovish]

Hello!

I am a fan of 8-bit microcomputers and an electronics hobbyist. I have built for my own use a cable for Commodore 128 that allows to view images from C128 on TV screen in 80 column mode and 40 column mode after proper switching. This cable is quite versatile as it supports these modes:

• 80 columns, RGBI color;
• 80 Columns Monochrome;
• 40 column Composite Video;
• 40 columns S-Video (additionally, it is possible to use ChromaFIX - 300Ohm resistor).

In my cable it is possible to control color saturation, separately for each component of primary colors (RGB) and separately the effect of Intensity on each color component.

I am wondering about a version with improvement of some colors, such as brown (dark-yellow in RGBI=1100) and dark gray (in RGBI=0001), which look bad on most screens. I know that some CGA monitors automatically corrected the dark-yellow to brown.

I found a project on the internet that uses TTL ICs (74LS244, 74LS138 and 74LS86) to correct such colors, but I liked more your project that uses the ATF16V8BQL (GAL16V8) chip. I programmed the GAL16V8D chip, with the Jedec file from your project, and analyzed how the output colors are set based on the RGBI data. Since I would like to have more control, over the output signals, and I am not yet able to create a PLD file myself, could I ask for the file with which you created your Jedec (JED) file?

Best regards Andrzej Bogacz (Yovish) from Poland abogacz.pl@gmail.com

Translated with www.DeepL.com/Translator (free version)

[JDet-74]

Hello Andrzej,

it looks like you are using a resistor ladder with some diodes for converting the RGBI signal to RGB signal. Is it something like that, what H2Obsession did? https://sites.google.com/site/h2obsession/CBM/C128/rgbi-to-scart

I just used the GAL to convert the 4 bit RGBI color scheme to the 6 bit (2 bit each color) RGB color scheme.

Since I would like to have more control, over the output signals, and I am not yet able to create a PLD file myself, could I ask for the file with which you created your Jedec (JED) file?

To program the GAL I used the Windows Software WinCUPL.

Regards

Tilo

[yovish]

Hello again! And can I ask you to give me the PLD file created in WinCupl? I am not able to do that yet. Best regards Andrzej Bogacz (Yovish)

    Dnia 13 marca 2022 13:17 Kernelpanic ***@***.***> napisał(a):

Hello Andrzej, it looks like you are using a resistor ladder with some diodes for converting the RGBI signal to RGB signal.
Is it something like that, what H2Obsession did?
https://sites.google.com/site/h2obsession/CBM/C128/rgbi-to-scart I just used the GAL to convert the 4 bit RGBI color scheme to the 6 bit (2 bit each color) RGB color scheme.

Since I would like to have more control, over the output signals, and I am not yet able to create a PLD file myself, could I ask for the file with which you created your Jedec (JED) file?

To program the GAL I used the Windows Software WinCUPL. Regards Tilo

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