Nios® V Processor Reference Manual

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ID 683632
Date 4/01/2024
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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. 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

3.3.9. Error Correction Code (ECC)

The Nios® V/m processor core has the option to enable error detection and ECC status reporting for the RAM block, that is the Register file. Each RAM block has its source ID. When an ECC event occurs, the processor transmits the source ID and ECC status to the ECC interface.

  • If the ECC event is a correctable error, the processor continues to operate without correcting the error.
  • If the ECC event is an un-correctable error, the processor halts its current progress and stall. You need to reset either the processor core alone, or the entire system.
Note: To reset the processor core alone, you need to apply the Reset Request Interface to safely reset the Nios® V processor (cleared of any outstanding operations). To reset the entire system, you can use the hard reset interface instead.

The ECC interface allows external logic to monitor ECC errors from the Nios® V/m processor. The interface is a conduit, made up of the following output signals.

  • cpu_ecc_status : Indicates the error status
  • cpu_ecc_source : Indicates the error source.
Table 34.   cpu_ecc_status
2-bits Encoding Description Effects on Software
2’b00 No ECC event None
2’b01 Reserved Not Applicable
2’b10 Correctable single bit ECC error None
2’b11 Un-correctable ECC error Likely fatal and halts the processor.
Table 35.   cpu_ecc_source
4-bits Encoding ECC Source Available
4’b0000 No ECC event Always
4’b0001 General Purpose Register (GPR) Always
4’b0010 ~ 4’b1110 Other RAM Blocks Not Available
4’b1111 Reserved Not Applicable
Note: Due to a limitation with embedded memory blocks, the simulation model of Nios® V processor does not support ECC on Arria® 10 devices.
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