The 6809 is one of the architectures from the era of the 6502, 8051, and Z80. Specifically, it's Motorola's response to the 6502 eating the 6800's lunch, the sa

The 6809 is one of the architectures from the era of the 6502, 8051, and Z80. Specifically, it's Motorola's response to the 6502 eating the 6800's lunch, the same way the 8086 was Intel's response to the Z80 eating the 8080's lunch. I'm guessing they picked the 6809 because it's a lot more friendly to C than those other architectures.