Altera Nios II Custom - Manual (Page 5)

January 2011 Altera Corporation Nios II Custom Instruction User Guide
1. Nios II Custom Instruction Overview
When you design a system that includes an Altera Nios II embedded processor, you
can accelerate time-critical software algorithms by adding custom instructions to the
Nios II processor instruction set. Custom instructions allow you to reduce a complex
sequence of standard instructions to a single instruction implemented in hardware.
You can use this feature for a variety of applications, for example, to optimize
software inner loops for digital signal processing (DSP), packet header processing,
and computation-intensive applications. In SOPC Builder, the Nios II parameter
editor provides a GUI to add custom instructions to the Nios II processor. In Qsys,
each custom instruction is a separate component in the Qsys system. You can add as
many as 256 custom instructions to your system.
In SOPC Builder, the custom instruction logic connects directly to the Nios II
arithmetic logic unit (ALU) as shown in
Figure 1–1 .
This chapter contains the following sections:
■ “Custom Instruction Overview”
■ “Custom Instruction Types” on page 1–3
For information about the custom instruction software interface, refer to Chapter 2,
Software Interface . For step-by-step instructions for implementing a custom
instruction, refer to Chapter 3, Implementing a Nios II Custom Instruction in SOPC
Builder or Chapter 4, Implementing a Nios II Custom Instruction in Qsys .
Figure 1–1. Custom Instruction Logic Connects to the Nios II ALU in SOPC Builder Systems
Nios II Embedded Processor
+
-
&
<<
>>
Result
A
Nios II
ALU
B
Custom
Logic