Among the processors of the 65xx family, the 65816 processor has the most features. The 65816 is a 65c02 with more opcodes, thus the correct name is the 65c816. We tend to skip the c. The 65c02 and 65c816 remained on the market during year 2009, as products of Western Design Center.

The 65816 processor has a 24-bit address space and can do addition and subtraction of 16-bit integers. The 65816 is old technology; hackers who code for the 65816 will soon wish to instead have a better, more modern processor. ROM hackers know the 65816 as the central processor of the SNES. The machine code in SNES hacks is 65816 code (excepting code for coprocessors like the SPC-700). The SNES uses a model of 65816 stamped 5A22, which might be a custom processor with a 65816 core. The 5A22 has all 65816 instructions. Some documents use the name S-CPU for the 5A22.

65816 assemblers Edit

There are many 65816 assemblers, but three of them can assemble or patch ROM images following the SNES ROM layout. These three are:

• xkas
• wla-65816
• snescom

Wiki pages Edit

• 65816 processor flag
  • 6502 emulation mode
• 65816 machine code
• SNES header including the 65816 interrupt vectors

Mnemonics Edit

References Edit

• From Western Design Center:
  • Programming the 65816, a good introduction and primary reference to the 65816.
  • W65C816S Datasheet, available as w65c816s.pdf from WDC's Documentation.