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

Page 4/4
1 | 2 | 3 |

By crisag

Rookie (29)

crisag's picture

21-09-2022, 20:55

Just fixed the BUSSDIR. As I'm already enabling the VDPR/VDPW using the IOREQ combined to M1 and R/W pins, I just got the result of the VDPR and used to signal BUSSDIR. I hope it is right as it is apparently equivalent to what is documented on the MSX Hardware Technical Handbook (page 35).

Now a question for you all. I got the circuit to superimpose the video from the computer into the video generated by the cartridge/V9990. I need to feed external HSYNC/VSYNC into the V9990 HRESET/VRESET pins to sync and combine external and internal R, G, B using a mux controlled by the /Ys signal.

But we all know the signals I need are not available on the cartridge bus, so we need a way to get the video output from the computer into the cartridge via cable. What is the best way? Another RGB IN connector?

By crisag

Rookie (29)

crisag's picture

21-09-2022, 20:58

Also, testing here I noticed that some games keep something on the main MSX screen while V9990 is working to draw stuff on the secondary display. This will cause issues with the superimpose I believe. You will see a ghost image on the combined video. Sad

By sdsnatcher73

Prophet (3534)

sdsnatcher73's picture

21-09-2022, 21:46

crisag wrote:

Just fixed the BUSSDIR. As I'm already enabling the VDPR/VDPW using the IOREQ combined to M1 and R/W pins, I just got the result of the VDPR and used to signal BUSSDIR. I hope it is right as it is apparently equivalent to what is documented on the MSX Hardware Technical Handbook (page 35).

Now a question for you all. I got the circuit to superimpose the video from the computer into the video generated by the cartridge/V9990. I need to feed external HSYNC/VSYNC into the V9990 HRESET/VRESET pins to sync and combine external and internal R, G, B using a mux controlled by the /Ys signal.

But we all know the signals I need are not available on the cartridge bus, so we need a way to get the video output from the computer into the cartridge via cable. What is the best way? Another RGB IN connector?

Yes I thinks VGA RGB IN would work best (composite in for MSX1 would also be nice but probably only NTSC 60Hz is viable), please note that the MSX will not have H/V SYNC but CSYNC so it needs to be split before feeding into V9990. Obviously many older software do not take superimposed V9990+V99x8 into account. So like other MSX with superimpose functionality it’s best to have a toggle to enable/disable it. Possibly even have an option to feed the (V99x8) input directly to the output. You would have:

1. V9990 output only
2. Input straight to output
3. Superimposed input with V9990

It would be nice if software could switch the output mode as well (via I/O ports) or even a BIOS. If we consider that MSX is to be connected to input and monitor to output than option 2 above would be start up mode I guess.

Page 4/4
1 | 2 | 3 |