Scanline timing diagram

Posted by , 27 September 2005 · 55 views

I don't know if this has been done before, but this diagram is the secret to my time-sensitive kernels. It shows every clock and every cycle of the scanline. No more adding up cycles. If you know what your kernel needs to do at a particular point, the code almost writes itself!I've attached a blank diagram, and an example filled out for the main part of Marble Jumper. I'll take suggestions for improvement, and if it seems useful to enough people, it could go in the MiniDig.

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vdub_bobby
Sep 27 2005 9:09 AM

That's a really nice diagram, Zach.

It might be nice to add arrows (or something) for when graphics writes need to happen. E.g., I'm pretty sure that you need at least a cycle lead time when writing to PF0, PF1, or PF2. In other words, writing to PF1 at cycle 28 will be too late; the write to PF1 needs to happen by cycle 27. This also applies to GRP0 and GRP1.

That doesn't apply to color writes, as far as I've been able to tell.

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EricBall
Sep 27 2005 9:21 AM

What I've done in the past is to put it in a simple spreadsheet which then makes it easier to shift sections of code around.

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supercat
Sep 27 2005 6:03 PM

EricBall, on Tue Sep 27, 2005 10:21 AM, said:

What I've done in the past is to put it in a simple spreadsheet which then makes it easier to shift sections of code around.

Once upon a time I used a Macintosh paint program to draw up a timing sheet with 76 cycles across, and with the playfield pixels marked. I may somewhere have a paper timing diagram from my first kernel which I did back in 1995 or thereabouts.

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cd-w
Sep 28 2005 3:09 AM

There is another nice timing diagram in this thread on the newbies forum.

Chris

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Robert M
Sep 30 2005 8:19 PM

I like your diagram. I like seeing the tools and techniques other people come up with to solve similar problems. Its a great way to see a problem from a new angle. For comparison, I posted my own timing diagram on the stella mailing list a while ago. Here's the link:

http://www.biglist.c...2/msg00180.html

Cheers!