Cortex-R4

The Arm Cortex-R4 processor is the smallest deeply embedded real-time processor based on the Armv7-R architecture.

Overview

The Cortex-R4 processor delivers high-performance, real-time responsiveness, reliability, and dependability with high error-resistance. It offers excellent energy efficiency and cost effectiveness for ASIC, ASSP, and MCU embedded applications.


Key benefits

  • Smallest Cortex-R processor providing high design flexibility to achieve excellent energy efficiency and system cost effectiveness.
  • Highly deterministic for fast interrupt handling in real-time applications.

  • Widely deployed real-time processor with fault containment built into the core.

Highlights

Architecture Armv7-R
Instruction Set Arm and Thumb-2. Supports DSP instructions optional Floating-Point Unit with single-precision.
Microarchitecture Eight-stage pipeline with instruction pre-fetch, branch prediction and selected dual-issue execution. Parallel execution paths for load-store, MAC, shift-ALU, divide and floating point. Binary compatibility with the Arm9 and Arm11 embedded processors.
Cache controllers Harvard memory architecture with optional integrated Instruction and Data cache controllers. Cache sizes are in-dependably configurable from 4 to 64 kB. Cache lines are either write-back or write-through.
Tightly-Coupled Memories Optional Tightly-Coupled Memory interfaces are used for highly deterministic or low-latency applications that may not respond well to caching ( e.g. instruction code for interrupt service routines and data that requires intense processing). One or two logical TCMs, A and B, can be used for any mix of code and data. TCM size can be up to 8 MB. TCM B has two physical ports, B0 and B1, for interleaving incoming DMA data streams.
Interrupt Interface Standard interrupt, IRQ, and non-maskable fast interrupt, FIQ and inputs are provided together with a VIC interrupt controller vector port. The GIC interrupt controller can also be used if more complex priority-based interrupt handling is required. The processor includes low-latency interrupt technology that allows long multi-cycle instructions to be interrupted and restarted. Lengthy memory accesses are also deferred in certain circumstances. Worst-case interrupt response can be as low as 20-cycles using the FIQ alone.
Memory Protection Unit (MPU) Optional MPU configures attributes for either twelve or sixteen regions, each with resolution down to 32 Bytes. Regions can overlap, and the highest numbered region has highest priority.
Floating-Point Unit (FPU) Optional FPU implements the Arm Vector Floating Point architecture VFPv3 with 16 double-precision registers, compliant with IEEE 754. The FPU performance is optimized for single-precision calculations and has (optional) full support for double precision. Operations include add, subtract, multiply, divide, multiply and accumulate, square root, conversions between fixed and floating-point, and floating-point constant instructions.
ECC Optional single-bit error correction and double-bit error detection for cache and/or TCM memories with ECC bits. Single-bit soft errors automatically corrected by the processor. ECC protection possible on all external interfaces.
Parity Optional support for parity bit error detection in caches and/or TCMs.
Master AXI bus 64-bit AMBA AXI bus master for Level-2 memory and peripheral access.
Slave AXI bus Optional 64-bit AMBA AXI bus slave port allows DMA masters to access the dual-port TCM B interface for high speed streaming of data in and out of the processor.
Dual-core A dual-core processor configuration implements a redundant Cortex-R4 CPU in lock step with offset clocks and comparison logic for fault tolerant/fault detecting dependable systems.

Configuration Synthesizable Verilog RTL with facility to configure options for synthesis.
Debug Debug Access Port is provided. Functionality can be extended with DK-R4.
Trace An interface suitable for connection to CoreSight Embedded Trace Macrocell ETM R4 is present.

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Applications

The Cortex-R4 is used extensively in high-volume, deeply embedded SoC applications.

Automotive

Cameras

Hard-disk drive controllers

Wireless baseband processors


Key Features

Fast and high performance

The processor's 8-stage dual issue pipeline combined with instruction pre-fetch and branch prediction achieve fast instruction execution.

Highly Deterministic

Advanced features such as Tightly Coupled Memory (TCM), Vectored Interrupt Controller (VIC) port and Low Latency Interrupt Mode (LLIM) make the Cortex-R4 highly deterministic and enable accelerated interrupt entry.

Reliable - error handling built into the core

Integrated Memory Protection Unit (MPU), Error-correcting code (ECC) memory and dual-core lock-step configuration ensure Cortex-R4's reliability and ability to handle errors.

Energy and cost efficient

Supports a highly flexible and efficient two-cycle local memory interface, enabling SoC designers to minimize system cost and energy consumption.


Characteristics

Cortex-R4 Single Processor 28 nm HPM
Maximum clock frequency Above 1.4 GHz
Performance 1.68 / 2.03 / 2.45 DMIPS/MHz*
3.47 CoreMark/MHz**
Total area (Including Core+RAM+Routing) From 0.21 mm2
Efficiency From 62 DMIPS/mW

* The first result abides by all of the 'ground rules' laid out in the Dhrystone documentation, the second permits inlining of functions (not just the permitted C string libraries) while the third additionally permits simultaneous multifile compilation. All are with the original (K&R) v2.1 of Dhrystone.

** CFLAGS ="--endian=little --cpu=Cortex-R4 --fpu=None -Ohs --no_size_constraints"



Support

Arm training courses and on-site system-design advisory services enable licensees to efficiently integrate the Cortex-R4 processor into their design to realize maximum system performance with lowest risk and fastest time-to-market.

  • Cortex-R4 Technical Reference Manual

    In-depth technical manual for system designers, verification engineers and programmers who are using or building a Cortex-R4 based SoC.

    Technical Reference Manual
  • Cortex-R Series Programmer's Guide

    For software developers working in assembly language or C, this covers everything necessary to program Cortex-R series devices.

    Get the guide
  • Development Tools for Cortex-R Series

    DS-5 Development Studio and a range of 3rd party and open source tools support Cortex-R series software development.

    Software Tools for Cortex-R

  • Arm Design Reviews

    Arm's on-site design review service gives licensees confidence that their Cortex-R4 CPU is implemented efficiently, to provide maximum system performance, with lowest risk and fastest time-to-market.

    Explore Arm Design Reviews
  • Questions Request more information

    Learn more about Cortex-R4, Arm’s  smallest, deeply embedded real-time processor based on the Armv7-R architecture. Contact us to speak with our technical team.


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