Monday, August 3, 2009

Introduction to ARM7TDMI

The most significant evolution was introduction of the Thumb instruction set in ARMv4T (ARM7TDMI processor).
The ARM7TDMI was the first new range of processors introduced in 1995 by ARM. The ARM7 core has a Von-Neumann architecture, where both data and instructions use the same bus. The core has a three-stage pipeline and executes the architecture ARMv4T instruction set.
ARM7TDMI is a popular core and is used in many 32-bit embedded processors. It provides a very good performance-to-power ratio. The ARM7TDMI processor core has been licensed by many of the top semiconductor companies around the world and is the first core to include the Thumb instruction set, a fast multiply instruction, and the EmbeddedICE debug technology.
One significant variation in the ARM7 family is the ARM7TDMI-S. The ARM7TDMI-S has the same operating characteristics as a standard ARM7TDMI but is also synthesizable. ARM720T is the most flexible member of the ARM7 family because it includes an MMU. The presence of the MMU means the ARM720T is capable of handling the Linux and Microsoft embedded platform operating systems. The processor also includes a unified 8K cache. The vector table can be relocated to a higher address by setting a coprocessor 15 register. Another variation is the ARM7EJ-S processor, also synthesizable. ARM7EJ-S is quite different since it includes a five-stage pipeline and executes ARMv5TEJ instructions. This version of the ARM7 is the only one that provides both Java acceleration and the enhanced instructions but without any memory protection.
The ARM7TDMI core is a 32-bit embedded RISC processor delivered provide the best combination of performance, power and area characteristics. The ARM7TDMI core enables system designers to build embedded devices requiring small size, low power and high performance.

ARM7TDMI Features

  • 32/16-bit RISC architecture (ARM v4T).
  • 32-bit ARM instruction set for maximum performance and flexibility.
  • 16-bit Thumb instruction set for increased code density.
  • Unified bus interface, 32-bit data bus carries both instructions and data.
  • Three-stage pipeline.
  • 32-bit ALU.
  • Very small die size and low power consumption.
  • Fully static operation.
  • Coprocessor interface.
  • Extensive debug facilities (EmbeddedICE debug unit accessible via JTAG interface unit).
  • Generic layout can be ported to specific process technologies.
  • Unified memory bus simplifies SoC integration process.
  • ARM and Thumb instructions sets can be mixed with minimal overhead to support application requirements for speed and code density
  • Code written for ARM7TDMI-S is binary-compatible with other members of the ARM7 Family and forwards compatible with ARM9, ARM9E and ARM10 families, thus it's quite easy to port your design to higher level microcontroller or microprocessor
  • Static design and lower power consumption are essential for battery -powered devices
  • Instruction set can be extended for specific requirements using coprocessors
  • EmbeddedICE-RT and optional ETM units enable extensive, real-time debug facilities

Available ARM7TDMI Microcontrollers

There are many ARM7TDMI based microcontrollers families are available in the market. The most popular and commonly used are listed below.

  1. Analog Devices ADuC7xxx
  2. Atmel AT91SAM7
  3. Freescale MAC7100
  4. NXP LPC2xxx
  5. ST Micro STR710
  6. TI TMS470

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