Datasheet

MC68HC908GR8 — Rev 4.0 Technical Data
MOTOROLA Central Processing Unit (CPU) 139
Technical Data — MC68HC908GR8
Section 10. Central Processing Unit (CPU)
10.1 Contents
10.2 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
10.3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
10.4 CPU registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140
10.5 Arithmetic/logic unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . .145
10.6 Low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145
10.7 CPU during break interrupts . . . . . . . . . . . . . . . . . . . . . . . . . .146
10.8 Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
10.9 Opcode Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
10.2 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully
object-code-compatible version of the M68HC05 CPU. The CPU08
Reference Manual (Motorola document order number CPU08RM/AD)
contains a description of the CPU instruction set, addressing modes,
and architecture.
10.3 Features
• 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
Frees
cale Semiconductor,
I
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