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I've uploaded a new version with more accurate info and some
parts fixed. You can download it here:

http://www.wenet.net/~cgfm2/smsvdp.txt

My Homepage

Seems I can't upload anything without it getting corrupt,
try this link instead:

http://www.emucamp.com/cgfm2/smsvdp.txt

My Homepage

Quote

> I've uploaded a new version with more accurate info and some
> parts fixed. You can download it here:

Wow, that document is truely excellent. Even helped me find a few bugs I've had for a while.

I noticed you have very detailed information for NTSC display, but none for PAL. The closest I've been able to come to emulating a PAL machine is to make it have 311 lines instead of the 262.

Any idea if this is the correct behavior? Or where the extra lines might come in? (I guess the V counter could just jump back futhur after the active display is drawn.)

- Mike

NeoSMS Homepage

Quote

> I noticed you have very detailed information for NTSC display, but none for PAL. The closest I've been able to come to emulating a PAL machine is to make it have 311 lines instead of the 262.

Sorry to say, I don't have any information on PAL displays.
I do know that the vertical blanking period is longer, and
that each frame has 312 lines.

Quote

> Any idea if this is the correct behavior? Or where the extra lines might come in? (I guess the V counter could just jump back futhur after the active display is drawn.)

I agree that the V counter most likely jumps back farther.
If a PAL version of Out Run (SMS) existed, you could probably
verify this since Out Run has screwed up scrolling if the V
counter isn't emulated exactly.

At any rate, I'll try to dig up some PAL timing data for the
next version of the VDP docs.

Quote

>
> I've uploaded a new version with more accurate info and some
> parts fixed. You can download it here:

> http://www.wenet.net/~cgfm2/smsvdp.txt

I'll place a copy of the update VDP document in the Technical Documents section as soon as I can (it may be a few days, though.)

Eric Quinn

I noticed that your comment about the background color is still in this version of the doc. Unless I've completely missed the point (which is entirely possible), the bgcolor is used in the TOP and BOTTOM borders (above and below the active refresh), and it _IS_ used for blanking out the left column, contrary to what your doc says. (The bgcolor is taken from the sprite palette) All one has to do to observe this is to play just about any game on a real SMS -- Quartet is what I tested it on this morning, but Zillion, Penguin Land, Rastan, Alex Kidd in Miracle World, and others all clearly demonstrate this.

You're right tho, emulator's don't look WRONG when the bgcolor isn't used. But a real SMS _does_ use this. In CHASMS, since the windowed mode is locked at 256x192 (image is resizable tho), the top and bottom borders aren't drawn, but even in this case you can use the bgcolor for clearing the left column. In fullscreen mode in CHASMS, I use the bgcolor to fill any space surrounding the screen. This is also what MASSAGE does.

Actually, now that I think of it, I'm not sure if the bgcolor is used or not when the screen is blanked. I'll have to try to investigate this. It is defintely used on the left-column blank, however.

- vecna

Quote

>
> I noticed that your comment about the background color is still in this version of the doc. Unless I've completely missed the point (which is entirely possible), the bgcolor is used in the TOP and BOTTOM borders (above and below the active refresh), and it _IS_ used for blanking out the left column, contrary to what your doc says. (The bgcolor is taken from the sprite palette) All one has to do to observe this is to play just about any game on a real SMS -- Quartet is what I tested it on this morning, but Zillion, Penguin Land, Rastan, Alex Kidd in Miracle World, and others all clearly demonstrate this.

Sorry, I didn't write that part very clearly at all.

The backdrop color is used when the display is blanked, for
the leftmost column when it's blanked, and in the overscan area.

I was mentally making a comparison to the Genesis, which uses
the backdrop color for any pixel where there's no sprite or
background data. The SMS on the other hand uses color #0 of
whatever palette was selected for that area.

The left column thing was a genuine mistake, I had looked at
the source to my emulator and saw a black color being used,
but I had originally done that because some users said it was
an eyesore to have a huge colored stripe on the side of the
screen. :) Of course you'd never notice this on a real
SMS because the display edges tend to get cut off.

At any rate, I'll mention this for the sake of clarity next
time I update. I dunno if you want to go to the trouble of
emulating the overscan area, but you can think of it as a
288x224 box with the SMS display right in the middle. You
can only see that with a video capture card, or by
messing with the centering controls on a monitor. :)

So I *DID* completely miss the point! That's exactly why I put that little disclaimer in there. ^_~ I found it very peculiar that you had written such an immensely detailed VDP doc and not known this, but at the same time it struck me as odd to say that the backdrop color is not used at all, ever.

I agree it's a bit overkill to "emulate" the overscan area, but it seems a perfectly good use of the extra screen space (in fullscreen mode, or whatever) to fill with the border color. It's sort of whacked, but it adds that much more of to the atmosphere of the game. I remember some of the Penguin Land levels had some truly obnoxious bgcolors like bright pink, but that's the kind of thing I remember from playing these games when I was 7 years old. Ah well. ^_^

- vecna

Author	Message
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	New VDP docs (again) Posted: Thu Mar 30, 2000 4:47 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	I've uploaded a new version with more accurate info and some parts fixed. You can download it here: http://www.wenet.net/~cgfm2/smsvdp.txt My Homepage

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Oops... Posted: Thu Mar 30, 2000 5:36 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Seems I can't upload anything without it getting corrupt, try this link instead: http://www.emucamp.com/cgfm2/smsvdp.txt My Homepage

Michael Montague Guest	Posted: Thu Mar 30, 2000 7:25 pm
Michael Montague Guest	Quote > I've uploaded a new version with more accurate info and some > parts fixed. You can download it here: Wow, that document is truely excellent. Even helped me find a few bugs I've had for a while. I noticed you have very detailed information for NTSC display, but none for PAL. The closest I've been able to come to emulating a PAL machine is to make it have 311 lines instead of the 262. Any idea if this is the correct behavior? Or where the extra lines might come in? (I guess the V counter could just jump back futhur after the active display is drawn.) - Mike NeoSMS Homepage

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Thu Mar 30, 2000 10:50 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote > I noticed you have very detailed information for NTSC display, but none for PAL. The closest I've been able to come to emulating a PAL machine is to make it have 311 lines instead of the 262. Sorry to say, I don't have any information on PAL displays. I do know that the vertical blanking period is longer, and that each frame has 312 lines. Quote > Any idea if this is the correct behavior? Or where the extra lines might come in? (I guess the V counter could just jump back futhur after the active display is drawn.) I agree that the V counter most likely jumps back farther. If a PAL version of Out Run (SMS) existed, you could probably verify this since Out Run has screwed up scrolling if the V counter isn't emulated exactly. At any rate, I'll try to dig up some PAL timing data for the next version of the VDP docs.

Eric Guest	Posted: Thu Mar 30, 2000 11:05 pm
Eric Guest	Quote > > I've uploaded a new version with more accurate info and some > parts fixed. You can download it here: > http://www.wenet.net/~cgfm2/smsvdp.txt I'll place a copy of the update VDP document in the Technical Documents section as soon as I can (it may be a few days, though.) Eric Quinn

vecna Guest	A quick note.. Posted: Thu Mar 30, 2000 11:52 pm
vecna Guest	I noticed that your comment about the background color is still in this version of the doc. Unless I've completely missed the point (which is entirely possible), the bgcolor is used in the TOP and BOTTOM borders (above and below the active refresh), and it _IS_ used for blanking out the left column, contrary to what your doc says. (The bgcolor is taken from the sprite palette) All one has to do to observe this is to play just about any game on a real SMS -- Quartet is what I tested it on this morning, but Zillion, Penguin Land, Rastan, Alex Kidd in Miracle World, and others all clearly demonstrate this. You're right tho, emulator's don't look WRONG when the bgcolor isn't used. But a real SMS _does_ use this. In CHASMS, since the windowed mode is locked at 256x192 (image is resizable tho), the top and bottom borders aren't drawn, but even in this case you can use the bgcolor for clearing the left column. In fullscreen mode in CHASMS, I use the bgcolor to fill any space surrounding the screen. This is also what MASSAGE does. Actually, now that I think of it, I'm not sure if the bgcolor is used or not when the screen is blanked. I'll have to try to investigate this. It is defintely used on the left-column blank, however. - vecna

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Re: A quick note.. Posted: Fri Mar 31, 2000 3:13 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote > > I noticed that your comment about the background color is still in this version of the doc. Unless I've completely missed the point (which is entirely possible), the bgcolor is used in the TOP and BOTTOM borders (above and below the active refresh), and it _IS_ used for blanking out the left column, contrary to what your doc says. (The bgcolor is taken from the sprite palette) All one has to do to observe this is to play just about any game on a real SMS -- Quartet is what I tested it on this morning, but Zillion, Penguin Land, Rastan, Alex Kidd in Miracle World, and others all clearly demonstrate this. Sorry, I didn't write that part very clearly at all. The backdrop color is used when the display is blanked, for the leftmost column when it's blanked, and in the overscan area. I was mentally making a comparison to the Genesis, which uses the backdrop color for any pixel where there's no sprite or background data. The SMS on the other hand uses color #0 of whatever palette was selected for that area. The left column thing was a genuine mistake, I had looked at the source to my emulator and saw a black color being used, but I had originally done that because some users said it was an eyesore to have a huge colored stripe on the side of the screen. :) Of course you'd never notice this on a real SMS because the display edges tend to get cut off. At any rate, I'll mention this for the sake of clarity next time I update. I dunno if you want to go to the trouble of emulating the overscan area, but you can think of it as a 288x224 box with the SMS display right in the middle. You can only see that with a video capture card, or by messing with the centering controls on a monitor. :)

vecna Guest	Ahh... Posted: Sat Apr 01, 2000 3:08 am
vecna Guest	So I DID completely miss the point! That's exactly why I put that little disclaimer in there. ^_~ I found it very peculiar that you had written such an immensely detailed VDP doc and not known this, but at the same time it struck me as odd to say that the backdrop color is not used at all, ever. I agree it's a bit overkill to "emulate" the overscan area, but it seems a perfectly good use of the extra screen space (in fullscreen mode, or whatever) to fill with the border color. It's sort of whacked, but it adds that much more of to the atmosphere of the game. I remember some of the Penguin Land levels had some truly obnoxious bgcolors like bright pink, but that's the kind of thing I remember from playing these games when I was 7 years old. Ah well. ^_^ - vecna

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