Overview
See also: ARM architecture family and List of ARM processors
The ARM Cortex-R is a family of ARM cores implementing the R profile of the ARM architecture; that profile is designed for high performance hard real-time and safety critical applications. It is similar to the A profile for applications processing but adds features which make it more fault tolerant and suitable for use in hard real-time and safety critical applications.
Real time and safety critical features added include:
The Armv8-R architecture includes virtualization features similar to those introduced in the Armv7-A architecture. Two stages of MPU-based translation are provided to enable multiple operating systems to be isolated from one another under the control of a hypervisor.
Prior to the R82, introduced on 4 September 2020,1 the Cortex-R family did not have a memory management unit (MMU). Models prior to the R82 could not use virtual memory, which made them unsuitable for many applications, such as full-featured Linux.1 However, many real-time operating systems (RTOS), with an emphasis on total control, have traditionally regarded the lack of an MMU as a feature, not a bug.1 On the R82, it may be possible to run a traditional RTOS in parallel with a paged OS such as Linux, where Linux takes advantage of the MMU for flexibility, while the RTOS locks the MMU into a direct translation mode on pages assigned to the RTOS so as to retain full predictability for real-time functions.1
ARM license
Arm Holdings neither manufactures nor sells CPU devices based on its own designs, but rather licenses the core designs to interested parties. ARM offers a variety of licensing terms, varying in cost and deliverables. To all licensees, ARM provides an integrable 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 specific design goals, such as higher clock speed, lower power consumption, instruction set extensions, reduced die size, debug support, etc. To determine which components have been included in a particular ARM CPU chip, consult the manufacturer datasheet and related documentation.
