An Introduction to the ARM Cortex-M3 Processor
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An Introduction to the ARM Cortex-M3 Processor
Shyam Sadasivan October 2006
1. Introduction
System-on-chip solutions based on ARM embedded processors address many different market
segments including enterprise applications, automotive systems, home networking and wireless
technologies. The ARM Cortex™ family of processors provides a standard architecture to address
the broad performance spectrum required by these diverse technologies. The ARM Cortex family
includes processors based on the three distinct profiles of the ARMv7 architecture; the A profile for
sophisticated, high-end applications running open and complex operating systems; the R profile for
real-time systems; and the M profile optimized for cost-sensitive and microcontroller applications.
The Cortex-M3 processor is the first ARM processor based on the ARMv7-M architecture and has
been specifically designed to achieve high system performance in power- and cost-sensitive
embedded applications, such as microcontrollers, automotive body systems, industrial control
systems and wireless networking, while significantly simplifying programmability to make the ARM
architecture an option for even the simplest applications.
1.1 Higher performance through better efficiency
In order to achieve higher performance, processors can either work hard or work smart. Pushing
higher clock frequencies may increase performance but is also accompanied by higher power
consumption and design complexity. On the other hand, higher compute efficiency at slower clock
speeds results in simpler and lower power designs that can perform the same tasks. At the heart of
the Cortex-M3 processor is an advanced 3-stage pipeline core, based on the Harvard architecture,
that incorporates many new powerful features such as branch speculation, single cycle multiply and
hardware divide to deliver an exceptional Dhrystone benchmark performance of 1.25 DMIPS/MHz.
The Cortex-M3 processor also implements the new Thumb
®
-2 instruction set architecture, helping it
to be 70% more efficient per MHz than an ARM7TDMI-S
®
processor executing Thumb instructions,
and 35% more efficient than the ARM7TDMI-S processor executing ARM instructions, for the
Dhrystone benchmark.
1.2 Ease of use for quick and efficient application development
Reducing time-to-market and lowering development costs are critical criteria in the choice of
microcontrollers, and the ability to quickly and easily develop software is key to these requirements.
The Cortex-M3 processor has been designed to be fast and easy to program, with the users not
required to write any assembler code or have deep knowledge of the architecture to create simple
applications. The processor has a simplified stack-based programmer’s model which still maintains
compatibility with the traditional ARM architecture but is analogous to the systems employed by
legacy 8- and 16-bit architectures, making the transition to 32-bit easier. Additionally a hardware-
based interrupt scheme means that writing interrupt service routines (handlers) becomes trivial, and
that start-up code is now significantly simplified as no assembler code register manipulation is
required.
Key new features in the underlying Thumb-2 Instruction Set Architecture (ISA) implement C code
more naturally, with native bitfield manipulation, hardware division and If/Then instructions. Further,
from a development perspective, Thumb-2 instructions speed up development and simplify long
term maintenance and support of compiled objects through automatic optimization for both
performance and code density, without the need for complex interworking between code compiled
for ARM or Thumb modes. The effect of this is that users can maintain their code in C and not have
to create libraries of pre-compiled object code, allowing for far greater code reuse.
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zsh74352014-08-25很好，可用。
