[stella] Qb/playfield timing

Subject: [stella] Qb/playfield timing
From: Glenn Saunders <cybpunks@xxxxxxxxxxxx>
Date: Mon, 05 Feb 2001 20:36:31 -0800
For the record, what is the right cycle count after WSYNC to rewrite the playfield registers for the right half of the screen?

I took a look at Qb and I'm trying to understand the cycle count notations.

        ; right pf
        lda playfield+2,x       ; 4
        sta PF0                 ; 3             < 49 (now@42)
        lda TargetDisplayL,y    ; 3
        sta PF1                 ; 3             < 55 (now@48)
        lda TargetDisplayR,y    ; 3
        sta PF2                 ; 3             < 66 (now@54)

Does this mean that
PF0 must be rewritten somewhere around cycle count 42-49,
PF1 between cycle count 43-55, and
PF2 somewhere between 54 and 66?

I'm just wondering what the exact min-max cyclecounts for each write so I can maximize time for inserting the sprite register routines in my game.

I can surely experiment, and probably will, but I was hoping this was documented somewhere already.

Also, I am having trouble digging up the INV sources from the archives. Could someone point me in the right direction?

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