Scrolling - 8bit Atari

[Jetboot Jack]

Hi!

 

Does anyone have a "nice" VBI vertical scrolling routine they would like to share?

 

sTeVE

[Wrathchild]

Hi Steve,

 

Depends on what you are scrolling?

If you have a graphics mode (line at a time) memory layout

then get the VBI to adjust the dlist's 'load memory' pointer, e.g.

 

DLIST:

.byte $70,$70,$70,$4E

LM_PTR:

.word SCR_MEM

.byte $0E,$0E etc

 

You can get clever and shuffle some LM pointers through the dlist

such that you reuse the memory you're not displaying

 

In a character based display you'll need to use the scroll

registers to scroll things smoothly and then adjust the LM

pointer(s) when reseting the scroll register.

 

Regards,

 

Mark

[Jetboot Jack]

Mark,

 

I have several simple MC scrolling routines that I'm tinkering with, but was wondering if anyone has a favorite for a 40 or 48 byte wide screen, using data laid out contigiously in RAM...

 

My horizontal routines were never very good, so I thought I'd tackle some vertical ones and was wondering if anyone had a "best"....

 

sTeVE