Hi. Just to let u know that I have made a 64 color, 240 x 200 resolution video game station with an ATMEGA64. Its a project I have made the last year, I was supposed to post in this forum, but I dont have a lot of free time... So I completed a web site just to show you the game console.
The console graphic is comparable to the Nintendo and the video output is a regular NTSC color composite output. (can be viewed on a standard NTSC tv or monitor with video input)
The sound is 2 voices PWM square wave channels with complete music playback capability. All the video timing stuff, color bitbang and audio routine are made in background by a complexe interrupt routine. So the final game maker dont have to take care of precise video timing/color stuff.
the CPU run at 20 Mhz.. A little bit overclocked, but its not a commercial project and the Atmega64 is capable of it (The new atmega serie are all at 20 mhz and use the same core making process...) Anyway... With all the video generation timing stuff process in the background, the main routine have a good 4.5 mhz left to do the game process.
The Mega64 is helped with a low cost CPLD (about 1$) to do just the video phasing stuff (with a 3.58 MHz Crystal). I have made this with discret logic at start, but take too much place on the PCB, so I decided to embeded it in a CPLD.
Here is a link to a fast made web page, you have screenshot, and 2 videos. Here I have included a screenshot of the Super Mario bros clone I have made on the videogame station and frogger game.
I dont have time to put technical detail at the moment, but feel free to ask.
here is the web site link to view the video and screenshot: