ARM provides the microcontroller solution

Development of the ARM architecture by Acorn was begun in 1983 as a cost-effective successor to existing 6502 systems. The ARM architecture had a simple yet efficient instruction set which enabled a compact silicon footprint, fast execution speed and low power. Acorn recognized the potential of this architecture and, in conjunction with a group of funding partners which included Apple and VLSI, created an independent enterprise in 1990 called ARM. With processor shipments to date of over 10 billion units, the ARM architecture has grown to become the most popular RISC architecture on the planet.

ARM processors have been used in numerous designs and ARM technology has become ubiquitous in mobile phones, MP3 players, PDAs, cameras, and navigation devices. ARM processors are also found in automotive products, medical devices and industrial control applications.

Today, more and more leading semiconductor manufacturers have used an ARM processor as the basis for their microcontroller line-up. Using an ARM processor allows a semiconductor company to focus on the most important aspects of the microcontroller, such as the application peripherals, flash memory integration and power consumption rather than trying to maintain pace on a treadmill of CPU development.

ARM has a common instruction set and integrated on-chip debug functionality which enables the reuse of many tool chain components from one design to another. Furthermore, the reuse of software components and tool chain know-how can reduce development times for future projects.

The ARM architecture is a RISC implementation with the following instruction sets:

- With the original ARM instruction set all instructions are 32-bits long. Most instructions provide conditional execution which avoids branch overhead associated with, for example, if/else statements.

- With the introduction of the ARM7TDMI processor came the condensed Thumb® instruction set based on 16-bit instructions. Thumb instructions are short forms of frequently used 32-bit ARM instructions, and enable code size to be reduced in practice by approximately 30-40 percent.

- Most recently, as a result of customer feedback and to further simplify code development the Thumb-2 instruction set was released. The Thumb-2 instruction set supplements Thumb technology with many of the most popular ARM instructions and also enables conditional execution. Software engineers formed part of the core development team to ensure the instruction set was optimized for high-level language compilers (e.g. C/C++). In addition, Thumb-2 instructions address common embedded requirements such as bit manipulation and hardware division. In summary, the Thumb-2 instruction set combines the arithmetic performance of the ARM instruction set with the code density of Thumb instructions.

Some ARM processors also have instruction set extensions for DSP algorithms or a Floating Point (VFP) coprocessor to accelerate floating point arithmetic in accordance with the IEEE754 standard.