Generating colour bars with minimal resources

[ppppenguin]

Had another look at the multiplier today. I've now built a simple 8 bit (signed) x 6 bit (unsigned) multiplier that is 6 gated adders. I've put 2 registers in there to improve speed. Perhaps surprisingly this also improves denisty. It may be that the fitting tools tie themselves in knots when presented with a huge great lump of combinational logic, giving a poor result. I can't be bothered to see if an extra pipeline stage gives any improvement in density. I don't need it t go any faster. More pipelining means more registers used for both the pipeline and elsewhere as matching delays.

Haven't done anything about the low chroma yet but when I wind up the gain on the vectorscope I can get all the vectors in their correct boxes. Vectorscope previously checked with very accurate colour bars from my main SPG so I know it's spot on.

Don't know if I'll take this project any further but it's been quite interesting. If I wanted to do a more ambitious pattern generator with this CPLD the answer would be an interface to a SD card. With many GB of memory available one could store lots of single frames and even moving sequences as literal data. For PAL, this would mean storing 8 fields of data, even for a still picture, to avoid jumps in subcarrier phase. This is conceptually similar to the Richard Russell and ImoGen test ard generators which both stored literal data, albeit at a lower pixel clock rate and using standard flash chips.