There are quite a few resources you can find after searching for a bit e.g http://problemkaputt.de/pandocs.htm http://problemkaputt.de/pandocs.htm or http://stu

There are quite a few resources you can find after searching for a bit e.g http://problemkaputt.de/pandocs.htm http://problemkaputt.de/pandocs.htm or http://students.washington.edu/fidelp/galp/megaguides/GameBoyProgrammingManual.pdf http://students.washington.edu/fidelp/galp/megaguides/GameBo... (the latter one being the original manual for licensed developers)