Subject: Re: [stella] VDEL From: Eckhard Stolberg <Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx> Date: Tue, 25 Jul 2000 22:33:54 +0200 |
At 11:35 25.07.2000 -0700, you wrote: >Could someone write an overview of how VDEL is actually used in a kernel as >a vertical positioning system for me in such a way that I can just >paraphrase it into a voiceover? It seems that would be the easiest way to >do it. OK, lets define the situation: Each player graphics has two registers GRP0-A and GRP0-B, GRP1-A and GRP1-B. The VDEL register for a player decide whether the A or the B register gets used for display in a given line. The graphics from the A register gets copied into the B register when some data gets written into the A register of the other player. Therefore in a double scanline kernel you would in every scanline: check if the player has to be displayed. if so, check which line of graphics has to be displayed ... and write that out. if not, write out a blank graphics byte. You alternate between players in every scanline. Now lets have a look at two double scanlines. All four graphics registers are set to $00. GRP0 gets handles in the first scanline and GRP1 in the second scanline of each double scanline set: If you want to display player0 in line 3, you would turn off it's VDEL register and set it's verical position counter to the second line-set. If you want to display player0 in line 4, you would turn on it's VDEL register and set it's verical position counter to the second line-set. If you want to display player1 in line 3, you would turn on it's VDEL register and set it's verical position counter to the first line-set. If you want to display player1 in line 4, you would turn off it's VDEL register and set it's verical position counter to the second line-set. >I'm including a file here which is a shockwave flash that is supposed to >illustrate a 4-bit polynomial counter. That one didn't make it. >I would like to expand on this diagram to show how the TIA drives the >speaker with this type of counter, and how it performs sprite positioning >(via coarse and fine registers) in combination with the binary/decimal -> >poly value code. Sorry, I can't help you here. Did anyone here ever figure out how the poly counters relate to the TIA register? 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 -> |
---|---|---|
[stella] VDEL, Glenn Saunders | Thread | Re: [stella] VDEL, Mark De Smet |
Re: [stella] Visual questions, John K. Harvey | Date | Re: [stella] VDEL, Mark De Smet |
Month |