Subject: Re: [stella] TIA polynomials revisited From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx> Date: Fri, 5 Dec 2003 21:36:41 +0100 |
> I was wrong about the duty cycle; it is 13/31 or 13:18 > Numerous apologies. > > I had mode 3 and 15 slightly off. > static const int poly5[] = { // 5 bit LFSR [5 3] > 5, 3, 2, 1, 3, 1, 1, 1, 1, 4, 1, 2, 1, 1, 2, 2, -1 }; > static const int poly68[] = { // used by mode 15 > 5, 6, 4, 5, 10, 5, 3, 7, 4, 10, 6, 3, 6, 4, 9, 6, -1 }; This is the same poly as in your previous version. If it was off, what's the correct poly? You said that mode 15 is the same as mode 7 except that it is driving the div6 device instead of the div 2 device. I think this is achieved by using the CPU clock as the input into the 5-bit poly instead of the pixel clock. Also you said that the math for mode 7 works out to be the same as mode 9. So the output of the poly in mode 15 should be the same as the output of the 5 bit poly at a third of the speed. So the following should be correct, right? static const int poly93[] = { // used by mode 15 15, 9, 6, 3, 9, 3, 3, 3, 3, 12, 3, 6, 3, 3, -1 }; > static const int divisors[] = { // frequency dividers > 1, 1, 15, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 1 }; For mode 2 you have a divisor of 15. Since that isn't used anywhere else in the TIA audio circuit, I'm wondering if mode 2 actually has the 4-bit poly clocked by the output of the div31 device with it's 13:18 duty cycle. Since this device only changes it's state twice during it's 31 bits, this would be similar to a div15. Ciao, Eckhard Stolberg ---------------------------------------------------------------------------------------------- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
Current Thread |
---|
|
<- Previous | Index | Next -> |
---|---|---|
Re: [stella] Video/Computer Chess, A Braunsdorf | Thread | Re: [stella] TIA polynomials revisi, Adam Wozniak |
[stella] The Atari programming for , Joe Wiencis | Date | Re: RE: [stella] I need a little di, Dennis Debro |
Month |