Retrochallenge: The First Piece of Code

Alright, it’s not much to look at, but it’s a start.

This code generates ten seconds of 770Hz square wave, which is the tape header. It is both less compact and less elegant than the code that Woz wrote for the Apple 1 and Apple II, but for that I blame my inexperience (and the fact that Woz was a kind of 6502 savant who had no need for such niceties as assemblers). I hope that it is at least fairly easy to read and understand.

Next up is writing a sync bit, followed by shifting in data from memory and writing it to tape one bit at a time.