Nios® V Processor Reference Manual

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ID 683632
Date 10/02/2023
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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. Intel® 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. Memory and I/O Organization 2.3.5. Error Correction Code (ECC)
2.3.4. Memory and I/O Organization x
2.3.4.1. Instruction and Data Buses 2.3.4.2. Address Map
2.3.4.1. Instruction and Data Buses x
2.3.4.1.1. Instruction Manager Port 2.3.4.1.2. Data Manager Port
2.4. Programming Model x
2.4.1. Privilege Levels
2.4.1. Privilege Levels x
2.4.1.1. Machine Mode (M-mode)
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. Exception Controller 3.3.6. Interrupt Controller 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. Interrupt Controller x
3.3.6.1. Timer and Software Interrupt Module
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
3.3.8. RISC-V based Debug Module x
3.3.8.1. Debug Mode 3.3.8.2. Halt from Debug Module 3.3.8.3. Trigger 3.3.8.4. Abstract Commands in Debug Mode 3.3.8.5. Hardware/Software 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
3.5. 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. Reset and Debug Signals 4.3.7. Control and Status Registers 4.3.8. Exception Controller 4.3.9. Interrupt Controller 4.3.10. Memory and I/O Organization 4.3.11. RISC-V based Debug Module 4.3.12. Error Correction Code (ECC)
4.3.4. 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. Interrupt Controller x
4.3.9.1. Timer and Software Interrupt Module
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 Mode 4.3.11.2. Halt from Debug Module 4.3.11.3. Trigger 4.3.11.4. Abstract Commands in Debug Mode 4.3.11.5. Hardware/Software Interface
4.4. Programming Model x
4.4.1. Privilege Levels 4.4.2. Control and Status Registers (CSR) Mapping
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 x
4.4.2.1. Control and Status Register Field
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

4.3.10.4.3. Using Tightly Coupled Memory Effectively

A system can use TCM to achieve maximum performance for accessing a specific code or data section. For example, interrupt-intensive applications can place exception handler code into a TCM to minimize interrupt latency. Similarly, compute-intensive digital signal processing (DSP) applications can place data buffers into TCM for the fastest possible data access.

You can implement one or more of the following functions or modules using TCMs to enhance the performance of your system:

  • Constant access time with no arbitration delays.
  • Separate exception stack for use only while handling interrupts.
  • Fast data buffers
  • Fast sections of code:
    • Fast interrupt handler
    • Critical loop

If the application’s memory requirements are small enough to fit entirely on-chip, it is possible to use tightly coupled memory exclusively for code and data. Larger applications must selectively choose what to include in tightly coupled memory to maximize the cost-performance trade-off.

Consider the following design when using TCMs:

  • Strike a balance between the speed enhancement from caches with the higher speed enhancement from TCMs.
  • Divide the on-chip memory resources equitably for the best combination of TCMs and cache.
  • Locating any information (code or data) within TCMs eliminates cache overhead such as cache flushing, loading, or invalidating.
Note: Connecting Nios® V processor data manager to instruction TCM subordinate port is not applicable because the processor must be in WFI state before any write. Thus, instruction TCM cannot map into the processor’s data region, unlike Nios® II processor.
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