Search results

OK. So setting the VDP state to write to VRAM address 0 like this: MOVE.W #$4000,$C00004 MOVE.W #$0000,$C00004 is less efficient than: MOVE.L #$40000000,$C00004 In the second example, $0000 will be placed in the VDP_CONTROL MIRROR ($C00006)? Also, does this write high word, increment, write...

Hi, I was just wondering what the VDP port mirrors are and why they may be used? For example, why is there an address $C00002 that is the VDP Data Port (Mirror). The same goes for the VDP Control (Mirror), H/V Counter (Mirror) etc. Thank you!

Hello Again, I successfully resolved all my questions about horizontal interrupt technicalities. Just finished making a test program that displays 224 alternating red and blue lines by swapping the background color every horizontal interrupt. I'm trying another even more time sensitive...

Found out what I needed. Check out the first reply to this forum thread: VDP FIFO and DMA questions - SpritesMind.Net Scroll down a bit in the first scroll box and you will find someone far smarter than I has found the exact horizontal and vertical frequencies.

I've been working on a 68000 program that just counts the number of HBLANKs over 60 VBLANKs (which is 1 second) but I keep getting only 13,000 or so. Still figuring things out on that.

I'm not entirely sure how you would measure horizontal interrupt frequency from the master 53.693175MHz clock. I measured the VSYNC frequency (which I assume would be the same as vertical interrupt. Correct me if I'm wrong) from pin 41 on the VDP using a multi-meter. It came to the expected...

Thanks! I think I'll measure it too just to see. The SEGA documentation can be all over the place. Sorry I'm new to Genesis programming and TV technicalities. But would I measure the frequency of Horizontal Interrupts from VDP pin 43? I've attached an image. It's from this site. Thanks again.

I also have a source attached here that says a horizontal interrupt occurs every 63.7μs. This would give a frequency of: 1 / x = 0.0000637s x = 1 / 0.0000637s x = 15,698Hz So weird.

Thank you! I appreciate the response. I think you meant to say frame rate of 59.97 for NTSC. But 262.5 * 59.97 = 15,742Hz? Could anyone write out exactly how you got to the 15,734Hz | 15,625Hz frequency? Also how can you have half a line? Is there a resource anywhere that has this...

Hello, This is my first post on SEGA Xtreme forums. I have a question about what the frequency of horizontal interrupts on the SEGA Genesis is. I've heard from other sources that it's the standard NTSC 15,734Hz. However, I've calculated the frequency to be 15,720Hz instead. An NTSC Genesis has...