Altera Nios II User Manual page 120

4–16
1
All signals in Nios II custom instructions must have the Custom Instruction Slave
interface type. To guarantee the component editor automatically selects the Custom
Instruction Slave interface type for your signals correctly during import, begin your
signal names with the prefix ncs_. This prefix allows the component editor to
determine the connection point type: a Nios II custom instruction slave. For example,
if a custom instruction component has two data signals plus clock, reset, and result
signals, an appropriate set of signal names is ncs_dataa, ncs_datab, ncs_clk,
ncs_reset, and ncs_result.
f
A complete discussion of the hardware and software design process for custom
instructions is beyond the scope of this chapter. For full details on the topic of custom
instructions, including working example designs, refer to the
Instruction User
Altera-Provided Custom Instructions
The following sections describe the custom instructions Altera provides.
1
The Endian Converter Custom Instruction and Interrupt Vector Custom Instruction
are not available in Qsys. For information about converting SOPC Builder designs to
Qsys, refer to the
Floating Point Hardware 2 Custom Instruction
The Nios II processor offers a set of optional predefined custom instructions that
implement floating-point arithmetic operations. You can include these custom
instructions to support computation-intensive floating-point applications.
The Floating Point Hardware 2 Custom Instruction is a high performance component
with predefined custom instructions that implement single-precision floating-point
operations. This component offers improved performance with lower cycle counts for
addition, subtraction, multiplication and division, and also supports floating-point
operations such as square root, comparison, minimum/maximum, negate/absolute,
and conversion.
The Floating Point Hardware 2 component is composed of two custom instructions:
■ Combinational custom instruction—Implements the minimum, maximum, compare,
negate, and absolute operations.
■ Multi-cycle custom instruction—Implements the add, substract, multiply, divide,
square root, and convert operations.
The component has two slaves, one slave for the combinatorial custom instruction
and the other slave for the multi-cycle custom instruction.
The opcode extensions for the Floating Point Hardware 2 custom instructions are 224
through 255. Refer to
To add the Floating Point Hardware 2 custom instruction to the Nios II processor in
Qsys, select Floating Point Hardware 2 under Embedded Processors in the
Component Library tab. Connect the two slave interfaces to the Nios II custom
instruction master.
Nios II Processor Reference Handbook
Guide.
SOPC Builder to Qsys Migration
Table 2–3 on page 2–7
Chapter 4: Instantiating the Nios II Processor
Nios II Custom
Guidelines.
for details.
February 2014 Altera Corporation
Custom Instruction Tab