Re: [stella] PAL TIM64T values

Subject: Re: [stella] PAL TIM64T values
From: "Alex Herbert" <herbs64@xxxxxxxxxxx>
Date: Sun, 15 Aug 2004 15:47:59 +0100
> I'm trying to use TIM64T for easy T.V format conversions
> Here are the values I'm trying to use. The NTSC values
> work perfectly but the Kernel value for PAL is too high
>
>
> NTSC
> VERTICAL_BLANK = 46
> KERNEL = 228
> OVERSCAN = 35
>  TOTAL 262 lines
>
> PAL
> VERTICAL_BLANK = 57
> KERNEL = 270
> OVERSCAN  = 42
>  TOTAL 312 lines
>
> Has anyone succesfully used this method?


Hi,

Yes, but I used T1024T instead of TIM64T to time the kernel period.  Over 13
scanlines pass in each tick of the timer with divide by 1024, so it means
setting the timer a few scalines early to get it to time-out on the correct
scanline.  (I seem to remember it was 4 scanlines for NTSC, 2 for PAL.).

Something like this:

    lda    #PAL_FLAG
    beq    set_ktime_ntsc
set_ktime_pal
    lda    #KTIME_PAL
    sta    T1024
    bne    set_ktime_done
set_ktime_ntsc
    lda    #KTIME_NTSC
    sta    T1024
    sta    WSYNC
    sta    WSYNC
set_ktime_done
    sta    WSYNC
    sta    WSYNC
    ; kernel starts here


I actually ditched this in the end becuase I decided to display the same
number of lines for both PAL and NTSC modes.

Alex Herbert
www.herbs64.com


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