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What are the differences between ARMv7-A, ARMv7-R and ARMv7-M?

Applies to: ARMv7 Architecture

Answer

Version 7 of the ARM® architecture or "ARMv7" comprises three profiles:

There are lots of similarities between the A and R profiles so they are described together in the ARMv7-AR Architecture Reference Manual.

The M profile is described separately in the ARMv7-M Architecture Reference Manual.

Both manuals contain a section titled "Architecture versions, profiles and variants" that provides a brief summary of the A, R and M profiles. However, there is no exhaustive architecture profile feature lookup/comparison table available for checking every single difference between each profile.  This article aims to describe some of the main differences. There are a vast number of differences between the M profile and the A and R profiles. The fundamental differences in ARMv7-M are listed below:

Additionally, the A and R profiles offer lots of advanced features and extensions, which are not available in ARMv7-M, for example:

The A profile also provides the Security Extensions (branded as TrustZone®).

A full list of these architectural extensions is available in the section titled "Architecture extensions" from the ARMv7-AR Architecture Reference Manual.

Apart from the mammoth ARMv7-M and ARMv7-AR Architecture Reference Manuals, there is lots of other reading material available to help developers understand the key differences between the different architecture profiles and variants, for example:

Also, if you have a spare 45 minutes, ARM's Training Manager talks about the ARM architecture in the ARM "University Program, ARM Architecture Fundamentals" video available on ARM's YouTube channel.

Article last edited on: 2016-01-06 14:47:33

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