Nios® V Processor Reference Manual

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ID 683632
Date 1/27/2025
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Document Table of Contents
Document Table of Contents x
1. Overview 2. Nios® V/c Processor 3. Nios® V/m Processor 4. Nios® V/g Processor 5. Nios V Processor Reference Manual Archives 6. Document Revision History for the Nios® V Processor Reference Manual
1. Overview x
1.1. Quartus® Prime Software Support
2. Nios® V/c Processor x
2.1. Processor Performance Benchmarks 2.2. Processor Pipeline 2.3. Processor Architecture 2.4. Programming Model 2.5. Core Implementation
2.3. Processor Architecture x
2.3.1. General-Purpose Register File 2.3.2. Arithmetic Logic Unit 2.3.3. Reset and Debug Signals 2.3.4. Instruction Cycles 2.3.5. Memory and I/O Organization 2.3.6. Error Correction Code (ECC)
2.3.5. Memory and I/O Organization x
2.3.5.1. Instruction and Data Buses 2.3.5.2. Address Map
2.3.5.1. Instruction and Data Buses x
2.3.5.1.1. Instruction Manager Port 2.3.5.1.2. Data Manager Port 2.3.5.1.3. Choosing a Suitable Interface
2.4. Programming Model x
2.4.1. Privilege Levels
2.5. Core Implementation x
2.5.1. Instruction Set Reference
3. Nios® V/m Processor x
3.1. Processor Performance Benchmarks 3.2. Processor Pipeline 3.3. Processor Architecture 3.4. Programming Model 3.5. Core Implementation
3.1. Processor Performance Benchmarks x
3.1.1. Pipelined 3.1.2. Non-pipelined
3.2. Processor Pipeline x
3.2.1. Pipelined Architecture 3.2.2. Non-pipelined Architecture
3.3. Processor Architecture x
3.3.1. General-Purpose Register File 3.3.2. Arithmetic Logic Unit 3.3.3. Reset and Debug Signals 3.3.4. Control and Status Registers 3.3.5. Instruction Cycles 3.3.6. Trap Controller (CLINT) 3.3.7. Memory and I/O Organization 3.3.8. RISC-V based Debug Module 3.3.9. Error Correction Code (ECC)
3.3.6. Trap Controller (CLINT) x
3.3.6.1. Related Control and Status Register 3.3.6.2. Direct Mode 3.3.6.3. Vectored Mode
3.3.6.1. Related Control and Status Register x
3.3.6.1.1. Machine Status Register (mstatus) 3.3.6.1.2. Machine Trap-Vector Base-Address Register (mtvec) 3.3.6.1.3. Machine Interrupt Register (mip and mie) 3.3.6.1.4. Machine Exception Program Counter Register (mepc) 3.3.6.1.5. Machine Cause Register (mcause) 3.3.6.1.6. Machine Trap Value Register (mtval)
3.3.6.2. Direct Mode x
3.3.6.2.1. Hardware Implementation 3.3.6.2.2. Software Implementation
3.3.6.3. Vectored Mode x
3.3.6.3.1. Hardware Implementation 3.3.6.3.2. Software Implementation
3.3.7. Memory and I/O Organization x
3.3.7.1. Instruction and Data Buses 3.3.7.2. Address Map
3.3.7.1. Instruction and Data Buses x
3.3.7.1.1. Instruction Manager Port 3.3.7.1.2. Data Manager Port 3.3.7.1.3. Choosing a Suitable Interface
3.3.8. RISC-V based Debug Module x
3.3.8.1. Debug Module 3.3.8.2. Abstract Commands 3.3.8.3. Program Buffer 3.3.8.4. Debug Mode 3.3.8.5. Hardware Trigger Module 3.3.8.6. JTAG Debug Transport Module 3.3.8.7. Nios® V Processor Implementation
3.3.8.1. Debug Module x
3.3.8.1.1. Reset/Halt/Run Control 3.3.8.1.2. Hart States 3.3.8.1.3. Debug Module Register
3.3.8.2. Abstract Commands x
3.3.8.2.1. Access Register Command 3.3.8.2.2. Using Access Register Command
3.3.8.3. Program Buffer x
3.3.8.3.1. Using Program Buffer
3.3.8.4. Debug Mode x
3.3.8.4.1. Enter Debug Mode 3.3.8.4.2. Exit Debug Mode 3.3.8.4.3. Core Debug Registers
3.3.8.5. Hardware Trigger Module x
3.3.8.5.1. Trigger Registers 3.3.8.5.2. Type of Address/Data Match Triggers 3.3.8.5.3. Using Triggers
3.3.8.6. JTAG Debug Transport Module x
3.3.8.6.1. JTAG DTM Registers 3.3.8.6.2. Accessing Debug Module Interface
3.4. Programming Model x
3.4.1. Privilege Levels 3.4.2. Control and Status Registers (CSR) Mapping
3.4.1. Privilege Levels x
3.4.1.1. Machine Mode (M-mode) 3.4.1.2. Debug Mode (D-mode)
3.4.2. Control and Status Registers (CSR) Mapping x
3.4.2.1. Control and Status Register Field 3.4.2.2. Memory Mapped Registers Fields
3.5. Core Implementation x
3.5.1. Instruction Set Reference
4. Nios® V/g Processor x
4.1. Processor Performance Benchmarks 4.2. Processor Pipeline 4.3. Processor Architecture 4.4. Programming Model 4.5. Core Implementation
4.3. Processor Architecture x
4.3.1. General-Purpose Register File 4.3.2. Arithmetic Logic Unit 4.3.3. Multipy and Divide Units 4.3.4. Floating-Point Unit 4.3.5. Custom Instruction 4.3.6. Instruction Cycles 4.3.7. Reset and Debug Signals 4.3.8. Control and Status Registers 4.3.9. Trap Controller (CLINT) 4.3.10. Memory and I/O Organization 4.3.11. RISC-V based Debug Module 4.3.12. Error Correction Code (ECC) 4.3.13. Branch Prediction 4.3.14. Lockstep Module
4.3.4. Floating-Point Unit x
4.3.4.1. IEEE 754 Exception Conditions 4.3.4.2. Floating Point Operations
4.3.4.2. Floating Point Operations x
4.3.4.2.1. Floating Point Classification
4.3.9. Trap Controller (CLINT) x
4.3.9.1. Related Control and Status Register 4.3.9.2. Direct Mode 4.3.9.3. Vectored Mode
4.3.9.1. Related Control and Status Register x
4.3.9.1.1. Machine Status Register (mstatus) 4.3.9.1.2. Machine Trap-Vector Base-Address Register (mtvec) 4.3.9.1.3. Machine Interrupt Register (mip and mie) 4.3.9.1.4. Machine Exception Program Counter Register (mepc) 4.3.9.1.5. Machine Cause Register (mcause) 4.3.9.1.6. Machine Trap Value Register (mtval) 4.3.9.1.7. Machine Second Trap Value Register (mtval2)
4.3.9.2. Direct Mode x
4.3.9.2.1. Hardware Implementation 4.3.9.2.2. Software Implementation
4.3.9.3. Vectored Mode x
4.3.9.3.1. Hardware Implementation 4.3.9.3.2. Software Implementation
4.3.10. Memory and I/O Organization x
4.3.10.1. Instruction and Data Buses 4.3.10.2. Address Map 4.3.10.3. Cache Memory 4.3.10.4. Tightly Coupled Memory
4.3.10.1. Instruction and Data Buses x
4.3.10.1.1. Instruction Manager Port 4.3.10.1.2. Data Manager Port
4.3.10.3. Cache Memory x
4.3.10.3.1. Instruction Cache 4.3.10.3.2. Data Cache 4.3.10.3.3. Configurable Cache Memory 4.3.10.3.4. Bypassing Cache (Peripheral Region) 4.3.10.3.5. Using Cache Memory Effectively
4.3.10.4. Tightly Coupled Memory x
4.3.10.4.1. Instruction and Data Tightly Coupled Memory 4.3.10.4.2. Accessing Tightly Coupled Memory 4.3.10.4.3. Using Tightly Coupled Memory Effectively
4.3.11. RISC-V based Debug Module x
4.3.11.1. Debug Module 4.3.11.2. Abstract Commands 4.3.11.3. Program Buffer 4.3.11.4. Debug Mode 4.3.11.5. Hardware Trigger Module 4.3.11.6. JTAG Debug Transport Module 4.3.11.7. Nios® V Processor Implementation
4.3.11.1. Debug Module x
4.3.11.1.1. Reset/Halt/Run Control 4.3.11.1.2. Hart States 4.3.11.1.3. Debug Module Register
4.3.11.2. Abstract Commands x
4.3.11.2.1. Access Register Command 4.3.11.2.2. Using Access Register Command
4.3.11.3. Program Buffer x
4.3.11.3.1. Using Program Buffer
4.3.11.4. Debug Mode x
4.3.11.4.1. Enter Debug Mode 4.3.11.4.2. Exit Debug Mode 4.3.11.4.3. Core Debug Registers
4.3.11.5. Hardware Trigger Module x
4.3.11.5.1. Trigger Registers 4.3.11.5.2. Type of Address/Data Match Triggers 4.3.11.5.3. Using Triggers
4.3.11.6. JTAG Debug Transport Module x
4.3.11.6.1. JTAG DTM Registers 4.3.11.6.2. Accessing Debug Module Interface
4.3.12. Error Correction Code (ECC) x
4.3.12.1. ECC Interface 4.3.12.2. ECC Error Injection 4.3.12.3. Affected CSR during ECC Event
4.4. Programming Model x
4.4.1. Privilege Levels 4.4.2. Control and Status Registers (CSR) Mapping (CLINT)
4.4.1. Privilege Levels x
4.4.1.1. Machine Mode (M-mode) 4.4.1.2. Debug Mode (D-mode)
4.4.2. Control and Status Registers (CSR) Mapping (CLINT) x
4.4.2.1. Control and Status Register Field (CLINT) 4.4.2.2. Memory Mapped Registers Fields
4.5. Core Implementation x
4.5.1. Instruction Set Reference
1. Overview
2. Nios® V/c Processor
3. Nios® V/m Processor
4. Nios® V/g Processor
5. Nios V Processor Reference Manual Archives
6. Document Revision History for the Nios® V Processor Reference Manual

3.2.2. Non-pipelined Architecture

The Nios® V/m processor supports a non-pipelined datapath.

Table 22.  Processor Non-pipelined Stages
Stage Denotation Function
F Instruction fetch Pre-decode for register file read
D Instruction decode
  • Decode the instruction
  • Register file read data available
  • Hazard resolution and data forwarding
E Instruction execute
  • ALU operations
  • Memory address calculation
  • Branch resolution
  • CSR read/write
M Memory
  • Memory and multicycle operations
  • Register file write
  • Next PC logic
  • Branch redirection

The Nios® V/m processor implements the general-purpose register file using the M20K memory blocks. The processor takes one clock cycle to read from an M20K location. Therefore, the F-stage initiates register file reads so general-purpose register values are available in D-stage.

One instruction is available in the processor datapath at any time. Instructions flow from F-stage to M-stages without any stalls. Instruction and associated control logic are registered during D-stage, E-stage, and M-stage.

The processor requests the next instruction during the M-stage.

  • For single cycle instructions, the processor makes the request as soon as the single cycle instruction enters M-stage.
  • For multicycle instructions, the processor makes the request as soon as the multicycle instruction completes.
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