Step11: 68000 Motorola Processor

The speed is 7 Mhz (!)

The CPU is 16/32 bits (internal registers are 32 bits). There are 16 registers:

D0 to D8 : Data register

A0 to A8 : Adress register

SP (Stack pointer) is equivalent to A7.

There are 56 instructions. One instruction size can go from 16 bits to longer size.

For example:

Instruction «RTS» (Return from subroutine) is 0x4E75.

Instruction «NOP» (No operation) is 0x4E71.

Full list of instructions HERE.

The format for writing instruction is SOURCE,DEST. For example «Move #4,d0» will copy value 4 (source) to register D0 (destination). Some processor (like intel) used the inverse notation (Instruction Dest, source).

The CPU have 7 levels of «interuptions», we’ll see that later.