Are there some useful routines for displaying/managing text or graphics for the MC6847 CRTC(something compatible with EhBasic)? As i managed to get my video module working, i would now like to be able to use it properly.

Is there any computer based on the 6502, and that it uses the MC6847?

Wikipedia says acorn atom
http://en.wikipedia.org/wiki/Motorola_6847
http://www.old-computers.com/MUSEUM/computer.asp?c=80

Where could i find the Atom's os?

There's a zip file here
http://mdfs.net/Docs/Comp/Acorn/Atom/

The rom files need decompiling, any recommendations?

I've never used it but this got a mention the other day
http://myweb.tiscali.co.uk/pclare/DASMx/

There's also Ruud's disassembler
http://www.baltissen.org/newhtm/auto_dis.htm

Ill give it a try, i hope i will find the routines, if not, ill have to write them myself...

A few years ago I found some disassembled Acorn Atom ROMs, nicely commented. Since I can't find them on-line anymore, I put a copy on my web server:

Atom Basic
Atom OS

For the text/graphics routines, you'll need the OS ROM. Note that the Atom OS did not have code to write text in the graphic modes. There are however some plot routines (mode 0) that could use the special graphics characters in text mode to draw some (very low res) graphics.

That's excellent.

I've found a copy linked from here which is part of a Splitting the Atom book online describing the ROM


and nearby some more Atom resources
http://www.atomclub.nl/atom_handleidingen/utility.html Manuals for some utility ROMs?
http://www.atomclub.nl/software/ROMS.html some ROMs

Here's a suitable entry page - it's a mirror of Keith Howell's site (defunct)
http://www.atomclub.nl/sites/Fpga/www.h ... m/Atom.htm

I've used the 6845(very similar) in a monochrome graphics project for graphics routines, and it depends how you have the lower address lines hooked up to the video ram. This will determine how the graphics routines shift out the bits to display graphics.
You can manipulate the address bus order from 6847 to RAM so you have an Atari scheme or hook it up straight and have a C-64 scheme. You need to do some research, but I've written a fast plotting routine that was <128 bytes for the C-64.

That is usually the best route to get what you want.

Thanks a lot for the help, i think i will write them myself, but i will peak in the atoms os a bit...
As for the hardware, i connected all the lines normally, without any special patterns.

If you want to use a text-mode screen (which I suspect is what you want with EHbasic) study the Atom OS routine OSWRCH. It handles writing a character to screen, including changing from ASCII to the 6847 character set (lower case letters appear inverted) and detecting and acting on special characters (CR, LF, etc). It also includes functions for clearing and scrolling the screen and moving the cursor. It also implements a software cursor. The routine expects memory data bit 7 to be connected to the 6847's invert pin. This can be a permanent connection since the invert pin has no effect on pixel-mapped displays.

Study the Atom OS line drawing routines - they are supposed to be optimised for speed and so, while not the easiest to understand, do perform well.

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