Space Invaders Test Rom: Documented!

I have a Space Encounters PCB with Ram errors I've been fixing and thought it would be nice if the Space Invaders Test Rom available on the web would work for Space Encounters as well. After burning one and trying it out, I found out it kind of does (at least for the ram tests). The main problem is that Space Encounters has a hardware special effect that allows the screen to fade up to an all white screen. When the machine is powered up this is on by default and must be turned off by the program. Since Space Invaders doesn't have the feature it doesn't account for it and the text on the Space Invaders Test Rom is unreadable because of the white screen.

While looking at the code of the Space Invaders Rom in order to fix this problem, I decided I'd learn quite a bit about the hardware / software interaction of the 8080 pcbs by documenting its code.

So here it is: Space Invaders Test Rom Documented

Here is the zip containing the original binaries ready for burning to eproms: Space Invaders Test Rom

 

Here is my first quick and dirty hack for a Space Encounters Test Rom: Space Encounters Test Rom Hack

This binary is for a 2732 and simply adds a jump to a routine that turns off the white screen effect and jumps back to the other code. I hacked it together before I realized I was overwriting one of the character symbols with code so the "A" character is currently trashed. But it does work and allows you to see the screen for the ram tests. I plan to clean this up and create a more comprehensive Space Encounters Test Rom in the future...