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Computer Operation: 68HC12
The computer executes instructions consisting of opcodes and operands, which are stored sequentially in memory as binary numbers.
The 68HC12 instruction set contains 209 instructions.
The program counter (PC register) points to the next instruction to be executed.
The 68HC12 address bus is 16 bits wide so its PC register is a 16-bit register.
Operands may contain data or addresses.
The number of bytes of operands depends on the instruction.
A stored program computer merely does what it is told. The computer fetches an instruction, performs the tasks dictated by that instruction and then fetches the next instruction. The instructions are stored sequentially in memory and executed in a sequential manner unless program logic dictates a branch.
Nearly all computers use zero/one logic in the hardware and therefore store their instructions and data as binary numbers. Although values may be represented as hex or decimal numbers in a program, they are stored in memory in binary representation.