You have been recruited by the Star League to defend the frontier against Xur and the Ko-Dan armada.
--- Sorry, wrong topic. I loved that movie, though.
Greetings Atari Fans and Developers!
I am a computer programmer, no stranger to assembly language, yet I am new to the 6502 (or 6507, as it were) chip and - more to the point - cpu cycle counting. As such, my first Atari program is an exercise in timing.
I have attached my first program for your critiquing pleasure. Basically, the program displays colored lines in the background, each based on the current descending line count. However, that being only marginally interesting, it also changes the color as frequently as possible on the current scan line. Finally, just for fun, it tracks a cycle counter that is added to the current line number. The final effect is 11 scrolling color bands.
I have executed this program both in Z26 and Stella, and observed a couple of bugs that I am having trouble tracking down:
* At regular intervals there is a short period of increased velocity, as if the program is "catching up".
* There is a minor visual anomaly that results in the horizontal seems between scan lines being slightly crooked at times. This is probably related to the previous issue, and could very well be simply due to a limitation of the EMUs.
* The first color band is shorter than all the others, while the last is longer. I feel like this is just the nature of the alignment of the cycles, but I am curious if it can be fixed.
I haven't the means to dump this to a cart, but I do wonder if those behaviors would be the same on the actual device.
If any devs out there have some insight or general advice, I'd be glad to have it!
PS: This was part of the alphabet would look like if Q and R were eliminated.
PPS: I love the Topics Tags. We need more adoption of tags on the internet.