MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 79
Chapter 7 Central Processor Unit (CPU)

7.1 Introduction

The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of
the M68HC05 CPU. The CPU08 Reference Manual (document order number CPU08RM/AD) contains a
description of the CPU instruction set, addressing modes, and architecture.

7.2 Features

Features of the CPU include:
Object code fully upward-compatible with M68HC05 Family
16-bit stack pointer with stack manipulation instructions
16-bit index register with x-register manipulation instructions
8-MHz CPU internal bus frequency
64-Kbyte program/data memory space
16 addressing modes
Memory-to-memory data moves without using accumulator
Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions
Enhanced binary-coded decimal (BCD) data handling
Modular architecture with expandable internal bus definition for extension of addressing range
beyond 64 Kbytes
Low-power stop and wait modes

7.3 CPU Registers

Figure 7-1 shows the five CPU registers. CPU registers are not part of the memory map.