How does one scroll a SED1335 based graphic LCD?

Go To Last Post
3 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

This question applies to any SED1335, S1D13305, S1D13700, etc... based graphic LCD.

I've got my mega128 talking to the controller no problem. What I am getting confused by is scrolling.

It seems if you wish to vertically scroll a text screen you simply right a new starting address to the scroll register. Ok, that works. I can scroll up or down a line at a time.

But how would you scroll up indefinetly? With the above technique you would quickly run out of display memory. It can't be true that I have to keep my own display buffer in the mega's ram and re-write the whole screen for every scroll????? What the heck would be the point of their scroll register then? I know I'm missing something simple here.

I hope my question is clear. Does anyone have any experience with scrolling on one of these things?

TIA,
Shannon

Go electric!
Happy electric car owner / builder

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I always wondered how windows scrolled on an old vga card with only one 640x480 page. I assume your sed controller has a ram that holds several screenfulls. Lets assume text mode, but graphics mode is analogous. There is a 'starting address of screen' register. It starts at 0x0000. 16 chars per line, line 2 would start at 0x0010, so I guess just walk the screen window down thru display ram line by line. At some point you need to reload new stuff in the top part that has scrolled off the top.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

yeah that is what I figured. Basically that means I do have to keep a screen buffer handy in my processor RAM so that I can reload the screen eventually. I really expected the display RAM on the SED1335 to wrap around. As I see it the scroll register has no use unless you just want to scroll back and forth.

Do you know if any of the other LCD controllers have a scroll feature that is any better?

Go electric!
Happy electric car owner / builder