August 2010 Blog Posts

I think it's safe to say that you, I, and everyone else on the planet is now sick of talking about cycle counting.  We've already looked a little into coloring the background by setting the COLUBK address before a scanline is drawn.  But what about those pesky sprites? Right off the bat, let's get this out: there are no drawing routines.  Zip.  Nada.  None.  Let me qualify this.  We now live in the blissful days of GDI, DirectX, OpenGL, even Flash for f--k's (folk's?) sake!  We take for granted our DrawLine and FillEllipse methods, optionally hardware-driven matrix transforms,...

So, the last post was pretty long, running through basic kernels practically line-by-line to see how the 6507 instructs the TIA to do great things with our TV.  The remainder of our posts really, then, have to do simply with performing various functions on the 2600.  How do I show a sprite?  How do I position it on the screen?  Sounds, collisions, etc...This post, however, will be one last smackdown on the relationship between our machine cycles and the TV rastering.  This time, we're getting into cycle counting and troubleshooting our assembly code. If you've been farting around...

Ok, our last post showed us our first piece of Atari 2600 code: the “kernel” – what the Stella guide calls the main display loop.  In this post we’ll examine our initial kernel code and the modifications we made at the end of the last post, then try adding a sprite or two.  Baby steps.  We need to hammer into our heads this synchronization of our code with the TV.  With the 2600, it’s all apparently about timing... So, running our initial kernel in the Stella emulator should have produced the following:   Nothing to scream about,...