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Table of Contents
The Motorola 6809
The 6809 is a binary-incompatible evolution of the previous 68xx series CPU. Often designed the “best 8-bit CPU of all times”, it prefigures some of the features that will make the 68000 a success.
Technical description
Registers: * A and B: two 8-bit accumulators, useable as the 16-bit D * X and Y: two index registers, used as memory pointers * U and S: user and system stacks * CC: condition flags register * DP: direct-page pointer
Instruction set and addressing modes
This is already covered elsewhere on the internet. Do I need to repeat everything? http://www.maddes.net/m6809pm/
Interrupts
* Reset: at system reset. * NMI: non-maskable. * IRQ * FIQ: registers are not automatically saved (faster than IRQ, but needs manual save of used registers) * SWI1, 2, and 3: software interrupts triggered by the SWI instruction.
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Datasheet, programming manual
