Crasm is a portable assembler for several 8 bit processors,
initially written in 1987 for AmigaOS.
It supports the 6800, 6801, 6803, 6502, and Z80 microprocessors.
It comes with a number of small examples,
including the 6801 firmware of my first homemade modem,
and the famous 6502 Microchess
program1).