Embedded Systems Design Europe - February 2008 - (Page 36)

feature 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 %. ● 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 highlevel language compilers (e.g. C/C++). Table 1: ARM Processors for Microcontrollers Fig. 1: Components of the Keil RealView microcontroller fevelopment kit. 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. The instruction set continuity between both ARM and Thumb enables a unique proposition within the microcontroller industry. A user can qualify and reuse validated software libraries from one project to another within the same tool chain framework. This tool chain reuse can signiﬁcantly reduce ongoing IT maintenance costs across multiple projects and applications to maximize the company’s investment in software. The success of the ARM architecture has resulted in the establishment of the ARM Connected Community, the industry’s largest network of third party developers who offer development tools for ARM. An overview of these companies can be found on www.arm. com/community. In addition, the ARM architecture is supported through several open source projects, for example the GNU compiler, GDB debugger and Linux distributions. Some development tool vendors specialize in device speciﬁc support of ARM processor-based microcontrollers resulting in a complete end-to-end solution for software development. For example: ● The RealView Microcontroller Development Kit from Keil offers dedicated support for more than 250 standard microcontrollers and combines the RealView compiler, µVision Debugger/ IDE and the RTX RTOS Kernel. ● The Embedded Workbench for ARM from IAR supports nearly all ARM processors to program MCUs from almost every manufacturer. This kit can be used with a wide range of debug solutions including their own JLINK debugger. ● Many other manufacturers, for example Codesourcery, Hitex, iSYSTEM, ARM Processor ARM7TDMI ARM720/722T ARM920T ARM926EJ ARM946E ARM966E ARM1136J Cortex-M1 Cortex-M3 Cortex-R4(F) ISA Extensions ARM/Thumb ARM/Thumb ARM/Thumb ARM/Thumb ARM/Thumb ARM/Thumb ARM/Thumb Thumb Thumb-2 ARM/Thumb-2 Memory Interface CPU Clock MMU, Cache MMU, Cache MPU, Cache, TCM MPU, Cache, TCM TCM MMU, Cache MPU MPU, TCM, Cache Up to 100MHz Up to100MHz Up to 250MHz Up to250MHz Up to 250MHz Up to 250MHz Up to 550MHz Up to 100MHz Up to 150MHz Up to 400MHz Characteristics DSP extensions + Java engine DSP extensions DSP extensions Floating Point Co-processor Soft core optimized for FPGA CPU core integrating interrupt control system Provides necessary interface for dual-core safety architectures Cache: Accelerates aggregate memory access speed by storing recently accessed information from slower system memory in a closely coupled RAM. MMU (Memory Management Unit): enables virtual memory and is generally required for platform operating systems such as Windows CE or Linux. MPU (Memory Protection Unit): Administers the access to certain storage areas for safety-critical applications. TCM (Tightly Coupled Memory): fast RAM or Flash memory is directly connected with CPU. This avoids a cache and provides deterministic program execution. 36 JANUARY – FEBRUARY 2008 | embedded systems design europe | www.embedded.com/europe 035-036-037_ESDE.indd 36 6/02/08 17:04:39 http://www.embedded.com/europe

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Embedded Systems Design Europe - February 2008 Contents ARTEMIS and ENIAC Get Parlimentary Approval Product Teardown Videos Come On Screen Esterel and Abslnt Integrate Products Microsoft Opens Windows to Networked Embedded Applications Trango Embeds Virtualization Tool in Cavium's Multicore CPUs MindTree - ADI Develop Security DVR Platform NXP Extends Deal with ARM to Cover MCUs Automotive and Embedded to Dominate DATE 08 ZigBee Spec Gets Smart On Energy Updated Card Spec Provides for Power-On Boot The Basics of Embedded Multitasking On a PIC Cover Feature: The Art of FPGA Construction Is Symmetric Multiprocessing For You? Accelerating MATLAB Using MEX-Files ARM Provides the Microcontroller Solution Embedded World Advertising Contracts

Embedded Systems Design Europe - February 2008

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