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The ARM Cortex-R is a family of
32-bit In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculation ...
and
64-bit In computer architecture, 64-bit Integer (computer science), integers, memory addresses, or other Data (computing), data units are those that are 64 bits wide. Also, 64-bit central processing unit, CPUs and arithmetic logic unit, ALUs are those ...
RISC In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
ARM In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between th ...
processor cores licensed by
Arm Holdings Arm is a British semiconductor and software design company based in Cambridge, England. Its primary business is in the design of ARM processors (CPUs). It also designs other chips, provides software development tools under the DS-5, RealView an ...
. The cores are optimized for hard
real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...
and
safety-critical A safety-critical system (SCS) or life-critical system is a system whose failure or malfunction may result in one (or more) of the following outcomes: * death or serious injury to people * loss or severe damage to equipment/property * environme ...
applications. Cores in this family implement the ARM Real-time (R) profile, which is one of three architecture profiles, the other two being the Application (A) profile implemented by the
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 32-bit only cores: ARM Cortex-A5, ARM Cortex-A7, ARM Cortex-A8, ARM Cortex- ...
family and the Microcontroller (M) profile implemented by the
Cortex-M The ARM Cortex-M is a group of 32-bit RISC ARM processor cores licensed by Arm Holdings. These cores are optimized for low-cost and energy-efficient integrated circuits, which have been embedded in tens of billions of consumer devices. Thou ...
family. The ARM Cortex-R family of microprocessors currently consists of ARM Cortex-R4(F), ARM Cortex-R5(F), ARM Cortex-R7(F), ARM Cortex-R8(F), ARM Cortex-R52(F), and ARM Cortex-R82(F).


Overview

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:
Tightly coupled memory
(uncached memory with guaranteed fast access time) * Increased
exception handling In computing and computer programming, exception handling is the process of responding to the occurrence of ''exceptions'' – anomalous or exceptional conditions requiring special processing – during the execution of a program. In general, an ...
in hardware * Hardware division instructions *
Memory protection Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that ha ...
unit (MPU) * Deterministic interrupt handling as well as fast
non-maskable interrupt In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but ...
s * ECC on L1 cache and buses * Dual-core
lockstep In the United States, lockstep marching or simply lockstep is marching in a very close single file in such a way that the leg of each person in the file moves in the same way and at the same time as the corresponding leg of the person immediately ...
for CPU fault tolerance 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, the Cortex-R family did not have a
memory management unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical ad ...
(MMU). Models prior to the R82 could not use
virtual memory In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very l ...
, which made them unsuitable for many applications, such as full-featured
Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
. However, many
real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...
s (RTOS), with an emphasis on total control, have traditionally regarded the lack of an MMU as a feature, not a bug. 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.


ARM license

ARM Holdings Arm is a British semiconductor and software design company based in Cambridge, England. Its primary business is in the design of ARM processors (CPUs). It also designs other chips, provides software development tools under the DS-5, RealView an ...
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 integratable hardware description of the ARM core, as well as complete software development toolset and the right to sell manufactured
silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
containing the ARM CPU.


Silicon customization

Integrated device manufacturers (IDM) receive the ARM Processor IP as synthesizable RTL (written in
Verilog Verilog, standardized as IEEE 1364, is a hardware description language (HDL) used to model electronic systems. It is most commonly used in the design and verification of digital circuits at the register-transfer level of abstraction. It is also ...
). 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 a particular ARM CPU chip, consult the manufacturer datasheet and related documentation.


Applications

The Cortex-R is suitable for use in computer-controlled systems where very low latency and/or a high level of safety is required. An example of a hard real-time, safety critical application would be a modern electronic braking system in an automobile. The system not only needs to be fast and responsive to a plethora of sensor data input, but is also responsible for human safety. A failure of such a system could lead to severe injury or loss of life. Other examples of hard real-time and/or safety critical applications include: *
Medical device A medical device is any device intended to be used for medical purposes. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and effective with reasonable assura ...
*
Programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity tha ...
(PLC) *
Electronic control unit An electronic control unit (ECU), also known as an electronic control module (ECM), is an embedded system in automotive electronics that controls one or more of the electrical systems or subsystems in a car or other motor vehicle. Modern vehic ...
s (ECU) for a wide variety of applications *
Robotics Robotics is an interdisciplinary branch of computer science and engineering. Robotics involves design, construction, operation, and use of robots. The goal of robotics is to design machines that can help and assist humans. Robotics integrat ...
*
Avionics Avionics (a blend word, blend of ''aviation'' and ''electronics'') are the Electronics, electronic systems used on aircraft. Avionic systems include communications, Air navigation, navigation, the display and management of multiple systems, ...
*
Motion control Motion control is a sub-field of automation, encompassing the systems or sub-systems involved in moving parts of machines in a controlled manner. Motion control systems are extensively used in a variety of fields for automation purposes, includi ...


See also

*
ARM architecture ARM (stylised in lowercase as arm, formerly an acronym for Advanced RISC Machines and originally Acorn RISC Machine) is a family of reduced instruction set computer (RISC) instruction set architectures for computer processors, configured ...
*
Interrupt In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to ''interrupt'' currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, ...
,
Interrupt handler In computer systems programming, an interrupt handler, also known as an interrupt service routine or ISR, is a special block of code associated with a specific interrupt condition. Interrupt handlers are initiated by hardware interrupts, softwar ...
*
JTAG JTAG (named after the Joint Test Action Group which codified it) is an Technical standard, industry standard for verifying designs and testing printed circuit boards after manufacture. JTAG implements standards for on-chip instrumentation in ele ...
, SWD * List of ARM architectures and cores *
List of ARM Cortex-M development tools This is a list of development tools for 32-bit ARM Cortex-M-based microcontrollers, which consists of Cortex-M0, Cortex-M0+, Cortex-M1, Cortex-M3, Cortex-M4, Cortex-M7, Cortex-M23, Cortex-M33 cores. Development toolchains IDE, compiler, linker, de ...
*
Real-time operating system A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...
,
Comparison of real-time operating systems This is a list of real-time operating systems (RTOSs). This is an operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer p ...


References


External links

;ARM Cortex-R official documents * : ;Migrating
Migrating from MIPS to ARM
– arm.com
Migrating from PPC to ARM
– arm.com
Migrating from IA-32 (x86-32) to ARM
– arm.com ;Other

!--At least partially outdated, e.g. Cortex-M7 has optional cache (always in practice present?) and both can have longer pipelines, Cortex-R8 11-stage, and former 6-stage. Cortex-R52 "introduces an extra privilege level which provides support for a hypervisor."--> {{Clear Cortex-R ARM cores Real-time computing