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Forums > C64 Coding > Timing rasters with sprites over

2006-04-04 00:06

SIDWAVE
Account closed

Registered: Apr 2002
Posts: 2238

Timing rasters with sprites over

I am gone stuck in trying to get some rasters be stable under some sprites.

There are 8 sprites, not moving.

Here's what I have:

color .byte 0,6,14,1,14,6,0,14
timer .byte 4,3,5,5,10,4,5,1

ldy #4
_swap dey
bne _swap

ldx #0
_doit lda color,x
sta d020
sta d021
ldy timer,x
_wrap dey
bne _wrap
inx
cpx #8
bne _doit

I've never learned about the badlines, is it
something with that, if i wanna time these rasters ?

Thanks

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2006-04-11 15:19

MRT
Account closed

Registered: Sep 2005
Posts: 149

Well, there's your problem.
You're generating a bad-line when you set your raster colors.

Try this:
(this code takes 2 cc more!)

  lda $d012
  sbc #$03       ;no need for sec
  and #%00000111
  ora #%00011000
  sta $d011

If you can't handle the 2 extra clockcycles then try the following timing trick:
(using example values below)

on rasterline 40, do:

  lda $d012

then go to next rasterline in the following two lines of code

  and #%00000111
  ora #%00011000

on rasterline 41, do:

  sta $d012

2006-04-11 16:12

MRT
Account closed

Registered: Sep 2005
Posts: 149

Or even easier...

Try this:

  lda $d012
  and #%00000111
  eor #%00011100
  sta $d011

This takes exactly the same amount of cycles as your own routine, but makes sure that the first 3 bits of $d012 and $d011 aren't the same! (and therefore don't create a badline)

2006-04-12 07:48

Hein

Registered: Apr 2004
Posts: 942

or try a $d011 table, filled with goody goodlines.

lda nobad,x
sta $d011
lda color,x
sta $d020
sta $d021

2006-04-12 12:17

Oswald

Registered: Apr 2002
Posts: 5086

or drink a cofee with intensity.

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