AndesCore™ N25/N25F Overview

  • AndeStar™ V5 Instruction Set Architecture (ISA), compliant to RISC-V technology
  • Floating point extensions (N25F)
  • 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
  • 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™ N25/N25F 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. N25F also supports single and double precision floating point instructions and half precision load/store. N25/N25F 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.

N25/N25F'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 and WFI mode for low power and power management, and JTAG debug interface for development support.


  • Networking and Communications
  • Advanced Driver-Assistance Systems
  • Video and Image Processing
  • Storage and Media Streaming

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 Features Benefits
RISC-V RV32IMAC Instructions
  • State-of-the art ISA from latest developments in computer architecture
  • Industry standard and open architecture
For N25F:
  • 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) and User (U) Privilege levels Embedded systems with privilege protections
CPU Core
Key Features Benefits
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
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

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

Memory Subsystems
Key Features Benefits
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
  • 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: AXI with 64-bit data or AHB with 64 or 32-bit data User-selectable bus interface for optimal efficiency
Bus save port: AHB with 64 or 32-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 Features Benefits
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 Features Benefits
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
Core, Process N25, 28HPC+
Frequency (MHz) 50
Dynamic power (uW/MHz) 3.6
Area (mm2) 0.032
Core, Process N25, 28HPC+ N25F, 28HPC+
Frequency (MHz) 1000 1000
Dynamic power (uW/MHz) 4.1 6.6
Area (mm2) 0.033 0.089

* Base configuration, 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 Packages

N25/N25F with CPU Subsystem

  • Pre-integrated N25/N25F, PLIC, Debug Module and simulation-only encrypted Platform

N25/N25F with AHB Platform

N25/N25F with AXI Platform