TRH9000 - The Yamaha V9990 based open-source video card for the MSX

I've been busy with boring work stuff but had some time today to move this thing forward and update you all. I just published to github the prototype board I'm using to validate the main circuit and make some tests with different sync separators/rgb encoders. It is based on the work done by Alexey Wierzbowsky and was adapted to have pads for memory chips, V9990, and two different video chips. I'm testing the Sony RGB encoder (CXA2075M) and the TI Auto-Detecting SD/HD/PC Video Sync Separator (LMH1980) to generate the video signal and study options for superimpose.

Testing the circuit, I found a pin assignment problem on the memory chips that is now fixed. Still need to test a few things and planning to do that in the upcoming weeks.

I notice that on the old schematic (TRH9000_Schema_Revision_0.pdf) there is no connection to busdir. This means that on some computers and slot-expanders you are unable to do I/O reads.

Thank you both for catching the mistake and providing documentation. I'll implement the circuit to derive the BUSSDIR signal and update the project. Here is a picture of the current prototype. Of course, BUSSDIR is missing there. Fixing it asap.

if you are going to do a v9990 with an FPGA, why not make an HDMI output?

cool! is it a working prototype ?