ARM Cortex-A

The ARM Cortex-A is a group of 32-bit and 64-bit RISC ARM processor cores licensed by ARM Holdings. The cores are intended for application use. The group consists of the 32-bit ARM Cortex-A5, ARM Cortex-A7, ARM Cortex-A8, ARM Cortex-A9, ARM Cortex-A12, ARM Cortex-A15, and ARM Cortex-A17 MPCore,^[1] and the 64-bit ARM Cortex-A53, ARM Cortex-A57, and ARM Cortex-A72.

The 64-bit ARM Cortex-A cores implement the ARMv8-A profile of the ARMv8 architecture.

The 32-bit ARM Cortex-A cores implement the ARMv7-A profile of the ARMv7 architecture. The main distinguishing feature of the ARMv7-A profile, compared to the other two profiles, the ARMv7-R profile implemented by the ARM Cortex-R cores and the ARMv7-M profile implemented by most of the ARM Cortex-M cores, is that only the ARMv7-A profile includes a memory management unit (MMU).^[2] Many modern operating systems require a MMU to run.

Overview

ARM license

ARM Holdings neither manufactures nor sells CPU devices based on its own designs, but rather licenses the processor architecture to interested parties. ARM offers a variety of licensing terms, varying in cost and deliverables. To all licensees, ARM provides an integratable hardware description of the ARM core, as well as complete software development toolset, and the right to sell manufactured silicon containing the ARM CPU.

Silicon customization

Integrated device manufacturers (IDM) receive the ARM Processor IP as synthesizable RTL (written in Verilog). In this form, they have the ability to perform architectural level optimizations and extensions. This allows the manufacturer to achieve custom design goals, such as higher clock speed, very low power consumption, instruction set extensions, optimizations for size, debug support, etc. To determine which components have been included in an ARM IC chip, consult the manufacturer datasheet and related documentation.

Instruction sets

The Cortex-A5 / A7 / A8 / A9 / A12 / A15 / A17 cores implement the ARMv7-A architecture.^[1] The Cortex-A53 / A57 / A72 cores implement the ARMv8-A architecture.

Documentation

The amount of documentation for all ARM chips is daunting, especially for newcomers. The documentation for microcontrollers from past decades would easily be inclusive in a single document, but as chips have evolved so has the documentation grown. The total documentation is especially hard to grasp for all ARM chips since it consists of documents from the IC manufacturer and documents from CPU core vendor (ARM Holdings).

A typical top-down documentation tree is: high-level marketing slides, datasheet for the exact physical chip, a detailed reference manual that describes common peripherals and other aspects of physical chips within the same series, reference manual for the exact ARM core processor within the chip, reference manual for the ARM architecture of the core which includes detailed description of all instruction sets.

Documentation Tree (top to bottom)

1. IC Manufacturer Marketing Slides.
2. IC Manufacturer Datasheets.
3. IC Manufacturer Reference Manuals.
4. ARM Core Reference Manuals.
5. ARM Architecture Reference Manuals.^[1]

IC Manufacturers usually have additional documents, including: evaluation board user manuals, application notes, getting started with development software, software library documents, errata, and more.

See also

• Comparison of ARMv7-A cores
• Microcontroller, List of common microcontrollers
• Embedded system, Single-board microcontroller
• JTAG, SWD

References

External links

Wikimedia Commons has media related to ARM Cortex-A.

Official

• ARM Cortex-A official website
• ARM Cortex-A5
• ARM Cortex-A7
• ARM Cortex-A8
• ARM Cortex-A9
• ARM Cortex-A12
• ARM Cortex-A15
• ARM Cortex-A17
• ARM Cortex-A53
• ARM Cortex-A57
• ARM Cortex-A72

Quick Reference Cards

• Instructions: Thumb (1), ARM and Thumb-2 (2), Vector Floating-Point (3), arm.com
• Opcodes: Thumb (1, 2), ARM (3, 4), GNU Assembler Directives (5).