Mickey's Safari in Letterland shaking

Discuss emulation of the Nintendo Entertainment System and Famicom.

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Dwedit
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Re: Mickey's Safari in Letterland shaking

Post by Dwedit » Sun Mar 19, 2017 9:42 am

Those are equivalent. Just that your notes for 0-3 are leaving out the dummy nametable fetch, but are including the sprite fetch.
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tepples
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Re: Mickey's Safari in Letterland shaking

Post by tepples » Sun Mar 19, 2017 1:17 pm

Zepper wrote:
tepples wrote:257-260: Dummy nametable fetch. A12 is low
261-264: Sprite pattern fetch (1 of 8). A12 is high
265-268: Dummy nametable fetch. A12 is low
269-272: Sprite pattern fetch (2 of 8). A12 is high
My notes are a bit different... but from the wiki anyways.

Code: Select all

/* Cycles 257-320: Sprite fetches (8 sprites total, 8 cycles per sprite)
    * 0-3: Read the Y-coordinate(0), tile number(1), attributes(2), and X-coordinate(3) 
	 of the selected sprite from secondary OAM.
    * 4-7: Read the X-coordinate of the selected sprite from secondary OAM 4 times
    (while the PPU fetches the sprite tile data).
    * For the first empty sprite slot, this will consist of sprite #63's Y-coordinate followed by 3 $FF bytes; 
    for subsequent empty sprite slots, this will be four $FF bytes.
    */
Is this incorrect?
I was describing the activity on the PPU's external video memory bus. You're describing the activity on the internal OAM bus. Both appear correct to me.

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Zepper
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Re: Mickey's Safari in Letterland shaking

Post by Zepper » Wed Feb 12, 2020 3:45 pm

Back.

Just a quick note, "261-264: Sprite pattern fetch (1 of 8). A12 is high". Well, A12 is high IF the sprite tile bank set (second sprite byte) is $1000.

lidnariq
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Re: Mickey's Safari in Letterland shaking

Post by lidnariq » Wed Feb 12, 2020 3:51 pm

MC-ACC uses a ÷8 prescaler on PPU A12 instead of analog filtering, so reversed patterns will generate really wrong results with it. (34÷8 "scanlines"=4¼ per real scanline)

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