1. Nios II Custom Instruction Overview
2. Custom Instruction Hardware Interface
3. Custom Instruction Software Interface
4. Design Example: Cyclic Redundancy Check
5. Introduction to Nios® II Floating Point Custom Instructions
6. Nios II Floating Point Hardware 2 Component
7. Nios® II Floating Point Hardware (FPH1) Component
8. Document Revision History for Nios II Custom Instruction User Guide
4.1.1. Setting up the Environment for the CRC Example Design
4.1.2. Opening the Component Editor
4.1.3. Specifying the Custom Instruction Component Type
4.1.4. Displaying the Custom Instruction Block Symbol
4.1.5. Adding the CRC Custom Instruction HDL Files
4.1.6. Configuring the Custom Instruction Parameter Type
4.1.7. Setting Up the CRC Custom Instruction Interfaces
4.1.8. Configuring the Custom Instruction Signal Type
4.1.9. Saving and Adding the CRC Custom Instruction
4.1.10. Generating and Compiling the CRC Example System
6.1. Overview of the Floating Point Hardware 2 Component
6.2. Floating Point Hardware 2 IEEE 754 Compliance
6.3. IEEE 754 Exception Conditions with FPH2
6.4. Floating Point Hardware 2 Operations
6.5. Building the FPH2 Example Hardware
6.6. Building the FPH2 Example Software
6.7. FPH2 Implementation of GCC Options
6.8. Nios II FPH2 and the Newlib Library
6.9. C Macros for round(), fmins(), and fmaxs()
2.1.5. External Interface Custom Instructions
Nios II external interface custom instructions allow you to add an interface to communicate with logic outside of the processor’s datapath.
At system generation, conduits propagate out to the top level of the Platform Designer system, where external logic can access the signals. By enabling custom instruction logic to access memory external to the processor, external interface custom instructions extend the capabilities of the custom instruction logic.
Figure 9. Custom Instruction with External Interface
Custom instruction logic can perform various tasks such as storing intermediate results or reading memory to control the custom instruction operation. The conduit interface also provides a dedicated path for data to flow into or out of the processor. For example, custom instruction logic with an external interface can feed data directly from the processor’s register file to an external first-in first-out (FIFO) memory buffer.