tests on NES / famicom dev on real hardware / keyboards
make # build the assembler
build/nesasm keyboard.asm # assemble the asm to NES file
cp keyboard.nes /Volumes/NO\ NAME/ # copy it to the Everdrive SD card
diskutil unmount /Volumes/NO\ NAME/ # unmount the SD card
or
fceux keyboard.nes # to test in emulator (no keyboard support)
Keyboard details: https://wiki.nesdev.com/w/index.php/Family_BASIC_Keyboard
6502 help: http://www.6502.org/tutorials/6502opcodes.html#BCC