SocLib Components General Index

NiosII Processor Functional Description

This hardware component belongs to the NiosII embedded processor family designed for Altera® field programmable gate array (FPGA) devices. The NiosII processor is a configurable soft-core processor, as opposed to a fixed, off-the-shelf processor. “Configurable” means that features can be added or removed on a system-by-system basis to meet performance goals. Altera® offers three NiosII cores:

  • NiosII/f. The NiosII/f “fast” core is designed for fast performance.
  • NiosII/s. The NiosII/s “standard” core is designed for small size while maintaining performance.
  • NiosII/e. The NiosII/e “economy” core is designed to achieve the smallest possible core size.

This hardware component is only an ISS, which should be wrapped with a CABA or TLM-T Wrapper using the Iss2 utility component.

The simulation model is actually an instruction set simulator, organized as a three-stage pipeline:

  • First stage: instruction fetch, with access to the external instruction cache.
  • Second stage: instruction is executed with a possible access to the external data cache.
  • Third stage: read memory access is written back to registers

This component models the NiosII/f “fast” core. Its main functional specifications are the following:

  • Hardware multiplication and division are supported
  • Floating-point instructions are supported by the way of custom instructions
  • dynamic branch prediction is not supported
  • optional tightly-coupled memory for instructions and data is not supported
  • Load and store I/O instructions are not supported

Component definition

Available in source:trunk/soclib/soclib/iss/niosII/metadata/


NiosII has no parameters.

Uses( 'niosII')

NiosII Processor ISS Implementation

The implementation is in

Template parameters

This component has no template parameters.

Constructor parameters

     sc_module_name name,   //  Instance Name
     int  ident);           // processor id

Visible registers

The following internal registers define the processor internal state, and can be inspected:

  • r_pc : Program counter
  • m_instruction : Instruction register
  • r_gpr[i] : General-purpose registers ( 0 < i < 32)
  • r_ctr[i] : Control registers ( 0 < i < 6)


NiosII defines 32 interrupt-request inputs. The lowest number has the highest priority.


None, it is to the wrapper to provide them.

Last modified 13 years ago Last modified on Jan 18, 2010, 11:05:18 AM