I've been stuck on this for hours now, i found several problems with my code but after fixing them it still doesn't work... is the following invalid?
D = M // D = count value
M = -1 // set current 16 pixels to black
"@D" references a symbol
named D, so a RAM variable is allocated to and its address is set into the A register.
If what you want to do is set the A register to the value in the D register, you want "A=D". In this case, you can load M directly into A using "A=M".
If you want to, you may email me your code and I'll be happy to return comments.