3General Purpose Processors: Altera Nios II

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3-General Purpose Processors Altera Nios II
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Altera Nios II processor

• A 32-bit soft core processor from Altera
• Comes in three cores Fast, Standard, Light
• The three cores trade FPGA area and power
  consumption for speed of execution.
• Is a RISC, Harvard Architecture Simple
  instructions, separate data and instruction
  memories.
• Has 32 levels of interrupts.
• Uses the Avalon Bus interface
• Programs compiled using C/C compilers

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Nios II Architecture
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Three forms of Nios II

• Nios II/fThe Nios II/f fast core is designed
  for fast performance. As a result, this core
  presents the most configuration options allowing
  you to fine-tune the processor for performance.
• Nios II/sThe Nios II/s standard core is
  designed for small size while maintaining
  performance.
• Nios II/eThe Nios II/e economy core is
  designed to achieve the smallest possible core
  size. As a result, this core has a limited
  feature set, and many settings are not available
  when the Nios II/e core is selected.
• All three are available to you !

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Selection in SOPC
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Why use microprocessors?

• Alternatives field-programmable gate arrays
  (FPGAs), custom logic, etc.
• Microprocessors are often very efficient can use
  same logic to perform many different functions.
• Microprocessors simplify the design of families
  of products.

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The performance paradox

• Microprocessors use much more logic to implement
  a function than does custom logic.
• But microprocessors are often at least as fast
• heavily pipelined
• large design teams
• aggressive VLSI technology.

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Power

• Custom logic is a clear winner for low power
  devices.
• Modern microprocessors offer features to help
  control power consumption.
• Software design techniques can help reduce power
  consumption.

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Challenges in embedded system design

• How much hardware do we need?
• How big is the CPU? Memory?
• How do we meet our deadlines?
• Faster hardware or cleverer software?
• How do we minimize power?
• Turn off unnecessary logic?
• How to optimize speed?
• Reduce memory accesses?

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Design methodologies

• A procedure for designing a system.
• Understanding your methodology helps you ensure
  you didnt skip anything.
• Compilers, software engineering tools,
  computer-aided design (CAD) tools, etc., can be
  used to
• help automate methodology steps
• keep track of the methodology itself.
• Altera CAD tools Quartus 2 , SOPC, Nios II IDE.

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Design goals

• Performance.
• Overall speed, deadlines.
• Functionality and user interface.
• Manufacturing cost.
• Power consumption.
• Other requirements (physical size, etc.)

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Levels of abstraction
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Top-down vs. bottom-up

• Top-down design
• start from most abstract description
• work to most detailed.
• Bottom-up design
• work from small components to big system.
• Real design uses both techniques.

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Typical CAD design flow
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Designing hardware and software components

• Must spend time architecting the system before
  you start coding.
• Some components are ready-made, some can be
  modified from existing designs, others must be
  designed from scratch.
• Example SOPC for Hardware design and Nios 2 IDE
  for Software Design.

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SOPC

• System on a programmable chip a hardware
  development tool.
• Used for integrating various hardware components
  together like
• Microprocessors, such as the Nios II processor
• Timers
• Serial communication interfaces UART, SPI
• General purpose I/O
• Digital signal processing (DSP) functions
• Communications peripherals
• Interfaces to off-chip devices
• Memory controllers
• Buses and bridges
• Application-specific standard products (ASSP)
• Application-specific integrated circuits (ASIC)
• Processors
• Generates files in Verilog or VHDL which can be
  added to the Quartus 2 project.

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SOPC builder tool
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Example SOPC system
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SOPC system having NIOS
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Examples of embedded systems projects

• Network of sonar sensors to increase the warning
  time for tornadoes, flash floods, or other
  environment disturbances. Uses data acquisition
  systems which gather information from sonar
  sensors, which collect data and relay it over a
  network.
• Wireless sensor mote, reading data through UART
  port
• Sound data acquisition and recording into secured
  digital card (SD)
• TCP/IP network stack with encryption processor
  via Nios II.
• Embedded camera control, and VGA display.
• Wireless USB adapter, to communicate to remote
  stations.
• Bridging multiple network protocols to provide
  hardware interoperability. E.g. USB to Ethernet
  interface and vice versa.