Re: [stella] 6 digit score display and other ramblings

Subject: Re: [stella] 6 digit score display and other ramblings
From: emooney@xxxxxxxxxxxxxxxx (Erik Mooney)
Date: Mon, 16 Mar 1998 02:34:55 GMT
>I managed to get a 6 digit score display working
>today _without_ looking at anybody's code :)  I

Unless your routine displays the characters in a different place than the
standard routine (center of the screen), why?

>It's currently using 19 bytes of RAM - 12 for
>pointers to the "font" data, 6 for the score
>(one byte per digit - I know this could be reduced
>to 3 fairly easy, but I might want to use more
>than 16 different characters in each spot) and 1
>for temporary storage.
>How few bytes of RAM does the best 6 digit
>display use - or, rather than "best", "most

The standard routine (don't think there IS any other, since the standard
does it with no cycles to spare) uses the 12 bytes for the pointers plus
one for temp storage.  You can store the score data any way you like and
set up the pointers during vblank.  I'd probably recommend 3 bytes of BCD.

It uses indirect indexed addressing, so it has to use LDA for the loads...
for temp storage, STA zeropage / LDA zeropage is the same speed as
TAX/TXS/TSX, with the added flexibility of letting the load be into any of
the registers.

>I didn't have to do any tricky "delay by a line"
>sort of things for this routine - I think I picked
>up the idea somewhere that this was necessary...
>was I getting this routine mixed up with something

The standard routine uses it, and it doesn't actually delay by a line.
Search the archives for my message titled "The scores / 48-pixel highres
routine explained!".  (wow, close to a year since I did that...)

>What other classic A2600 routines are there to try
>to code?  I'm not wanting to try working on a full
>game yet - this is only my second little hack on
>the 2600, and would like to get a bit more familiar
>with the machine first.

Well, there's the old movable-sprite deal, if you haven't done that yet.
Can't think of any other widely-used routines off the top of my head.. best
I can come up with is a paddle-reading routine.  Another popular routine
around here, though I haven't tried it, is a flicker-reducing
multiple-sprite package.  Or you could try to make your score routine into
a movable 48-pixel sprite... if you can do that, we'll be groveling at your
feet :)

>And finally, here is my Atari 2600 development system:
>2 Commodore 1702 monitors
>C128(flat) with 512K REU
>FD-2000 (1.6 meg 3.5" disk drive)
>A2600 (4-button w/Supercharger)
>$5 VCR from the Salvation Army shop
>It's working really nicely - and the REU and fancy
>drive aren't necessary - this rest of the system could
>be purchased for $60 pretty easily :)

Er, okay... my dev system is my PC with emulators, a 6-switch 2600 with
Supercharger, and an old TV we found in the garage.

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