6560 FPGA Progress.

[beamrider]

Nice video. Thanks.

Looking forward to future episodes...

[JonBrawn]

The VIC (6560/6561) in fact has sepearate luma resistors for each colour, see for example this thread (partly in German)
https://www.forum64.de/index.php?thread ... ost1699320

I guess in the world that is FPGAs, I can say, "five colours get 50% luma output, that one and that and that one get 25%, black gets zero, white gets 100%, and the rest gets 75%, and sync gets negative-a-bit", and then mux that inside the FPGA to produce six drive outputs that could either use individual parallel resistors or a chain of series resistors - in my world it makes zero difference which you choose, but if you don't want to do all the muxing involved in turning sixteen colours plus sync into just six outputs because it will add transistors to do so, then sixteen resistors sure looks more attractive.

Suppose you implement the luma DAC in the way I've done it, with six resistors in a chain rather than six resistors in parallel. In that case, the resistors will have values that are closer to each other, and if fabricated in silicon, that might matter for some processes (I don't know).

In my defence, the only time I've seen the schematics of a luma signal generator of that era in real life, it did use a chain of resistors. I'm guessing that was monochrome only, though, so the story would be different.

[JonBrawn]

Nice video. Thanks.

Looking forward to future episodes...

I should have made a video about the board I've been working on to interface with the new FPGA development board I'm switching to. It would involve such epic scenes as "why are their connectors numbered backwards? There is no physical way of putting a connector with wire one connected to pin 1 on that board", "Why is nothing on that board aligned to a grid?", "what do you mean you can't plug cables into both connectors at the same time?" "KiCad 7 ate my PCB", and my favourite "The Gods smote my USB hub with thunderbolts from heaven".

Note to self: buy a new USB hub today.