I used to write and modify direct machine code on the 6805 variants. Until i finally got my hands on an assembler to make use of mnemonics. Made life easier. 

Everytime I added a block of machine code, I had to go and fix all the indirect/relative jump calls because of the now re-arranged addressing from moving things around/adding code. Thank god an assembler does all this for you. 

I used to be real heavy into 6805 programming/hacking back in the day. Not so much anymore. I havent messed with it in a few years. I moved over to AVR. It was funny, I used to dump integrated ROM code from 6805 stuff using a well-placed glitch.