AndesCore™ A25

Compact High-Speed 32-bit CPU for Real-time and Linux Applications

AndesCore™ A25 Overview

  • AndeStar™ V5 Instruction Set Architecture (ISA), compliant to RISC-V technology
  • DSP/SIMD ISA to boost the performance of digital signal processing
  • Floating point extensions
  • Andes extensions, architected for performance and functionality enhancements
  • Separately licensable Andes Custom Extension™ (ACE) for customized acceleration
  • 32-bit, 5-stage pipeline CPU architecture
  • 16/32-bit mixable instruction format for compacting code density
  • Branch predication to speed up control code
  • Return Address Stack (RAS) to speed up procedure returns
  • Memory Management Unit (MMU) and Physical Memory Protection (PMP)
  • Flexibly configurable Platform-Level Interrupt Controller (PLIC) for supporting wide range of system event scenarios
  • Enhancement of vectored interrupt handling for real-time performance
  • Advanced CoDense™ technology to reduce program code size

AndesCore™ A25 is a 32-bit CPU IP core based on AndeStar™ V5 architecture which incorporated RISC-V technology, it is capable of delivering high per-MHz performance and operating at high frequencies, at the same time it is small in gate count. A25 also supports the RISC-V P-extension (draft) DSP/SIMD ISA contributed by Andes, single- and double-precision floating point instructions, half-precision load/store and MMU for Linux based applications. A25 comes with options, including branch prediction for efficient branch execution, Instruction and Data caches, Local Memories for low-latency accesses, ECC for L1 memory soft error protection, and Andes Custom Extension™ (ACE) to add proprietary instructions to accelerate performance/power consumption critical spots.

A25’s 5-stage pipeline is optimized for high operating frequency and high performance. Features also includes PLIC and vectored interrupts for serving various types of system events, AXI 64-bit or AHB 64/32-bit bus, PowerBrake, QuickNap™ and WFI mode for low power and power management, and JTAG debug interface for development support.

Applications

  • Networking and Communications
  • Advanced Driver-Assistance Systems
  • Video and Image Processing
  • Smart wireless switch/router
  • Machine/Deep Learning acceleration

Block Diagram

Development Tools

  • AndeSight™ Integrated Development Environment
  • COPILOT: Custom-OPtimized Instruction deveLOpment Tool for ACE
  • ICE debugging hardware

Key Features and Performance

AndeStar™ V5 Architecture

Key FeaturesBenefits
RISC-V RV32IMACFDP instructions
  • State-of-the art ISA from latest developments in computer architecture
  • Industry standard and open architecture
RISC-V P-extension (draft) DSP/SIMD instructions with versatile operations Boost the performance of voice, audio, image and signal processing
  • RISC-V single and double precision floating point instruction
  • Andes half precision load/store extension
Accelerate the processing of high precision arithmetic
Andes Extended Instructions Andes exclusive performance and functionality enhancements
Andes Custom Extension™ (ACE) option to create customized instructions for software acceleration
  • Add customized instruction extensions to facilitate Domain-Specific Architecture/Acceleration (DSA)
  • Boost application performance significantly, at the same time maintain the programmability
  • Powerful constructs are available to define high level instruction
  • ACE design is based on Verilog and C languages which are familiar to the designers
  • The COPILOT tool automatically generates the extended CPU and software toolchain
  • Do not require expertise in processor pipeline to design ACE instructions
16/32-bit mixable instruction format For compact code density
32 general-purpose registers For better code size and performance
Machine (M), User (U) and Supervisor (S) Privilege levels For Linux and advanced operating systems with protection between kernel and user programs

CPU Core

Key FeaturesBenefits
2.85 DMIPS/MHz, 3.58 CoreMark/MHz* Superior performance-per-MHz
5-stage pipeline, with a full-cycle reserved for critical SRAM accesses Superior performance-efficiency, while allowing for high speeds

Extensive branch predication features

  • Branch Target Buffer (BTB): 32, 64, 128 or 256-entry
  • Branch History Table (BHT): 256-entry, with 8-bit branch history
  • Return Address Stack (RAS): 4-entry
  • Branch Target Buffer and Branch History Table to speed up control codes
  • Return Address Stack to speeds up procedure returns

Memory Management Unit

  • Sv32 virtual-memory systems
  • 4/8-entry fully associative ITLB/DTLB
  • 32/64/128-entry 4-way set-associative shared TLB
  • Hardware page table walker
  • Virtual memory support for full address space and easy code/data sharing
  • Support for full-featured OS such as Linux
  • Protection of supervisor and user privilege
  • Hardware for fast address translation
Physical Memory Protection (PMP), 16 regions Basic read/write/execute memory protection with minimum cost
Performance monitors Program code performance tuning
StackSafe™ hardware stack protection
  • Easy identification of stack size threshold during development
  • Hardware error detection of stack overflow and underflow at runtime

Multiplier options

  • Fast multiplier: pipelined, 2-cycle
  • Small multipliers: producing 1, 2, 4, or 8 bits per cycle
Option to choose between speed and area according to application's requirements
PowerBrake technology Performance throttling to digitally reduce power consumption
QuickNap™ technology Fast power-down/wake-up support for caches

* BSP v5.0.0, DMIPS/MHZ without no-inline option, best performances

Memory Subsystems

Key FeaturesBenefits

I-Cache & D-Cache

  • Size: 8KB to 64KB
  • Set associativity: Direct-mapped, 2-way or 4-way
  • Accelerating accesses to slow memories
  • Flexible cache configurations

ILM & DLM

  • Size: 4KB to 16M
  • SRAM or AHB-Lite interface support
  • Bus masters accesses by AHB slave port
  • For deterministic and efficient program execution
  • Flexible size selection to fit diversified needs
Soft-error protection: ECC or parity for I-Cache and D-Cache, ILM and DLM with SRAM interface Code and data integrity protection
Bus master port: AHB or AXI with 64-bit data, 32 to 64-bit address User-selectable bus interface for optimal efficiency
Bus save port: AHB with 64-bit data, for ILM/DLM accesses Efficient data transfer between CPU and SoC masters
Core/bus clock ratio of N:1 Simplified SoC integration

Platform-Level Interrupt Controller (PLIC)

Key FeaturesBenefits

Implements RISC-V PLIC specification

  • Up to 1023 PLIC interrupt sources
  • Up to 255 PLIC interrupt priority levels
  • Up to 16 PLIC interrupt targets
Allow individual interrupts to be serviced and prioritized without sharing

Enhanced interrupt features

  • Vectored interrupt dispatch
  • Priority-based preemption
  • Selectable edge trigger or level trigger
  • Faster interrupt handling for real-time applications
  • Complete hardware preemption support for faster response
  • Flexible interrupt source interface for simpler SoC design

Debug Support

Key FeaturesBenefits
Implements RISC-V debug specifications Supported by industry debug tool suppliers
JTAG Debug Port Industry-standard support
Embedded Debug Module with up to 8 triggers Flexible configurations to tradeoff between gate count and debugging capabilities
Exception redirection support Entering debugger upon selected exceptions without using breakpoints

Performance

Core, ProcessA25 (w/o DSP, FPU), 28HPC+A25 (with DSP, FPU), 28HPC+
Frequency (MHz) 1000 1000
Dynamic power (uW/MHz) 17 20
Area (mm2) 0.084 0.165

* Configured with cache and MMU. RVT 9-track library, SS corner, 0.81V, -40°C, and with I/O constraint. Power consumption at TT corner, 0.9V, 25°C

Product Package

A25 with AXI Platform