xa: xa (Andre Fachat's open-source 6502 cross assembler) xa: xa: xa is a high-speed, two-pass, portable cross-assembler. It understands xa: mnemonics and generates code for NMOS 6502s (such as 6502A, 6504, xa: 6507, 6510, 7501, 8500, 8501, 8502 ...), CMOS 6502s (65C02, Rockwell xa: R65C02) and the 65816. xa: xa: xa: xa: xa: