Designing Embedded Hardware01. Introduction of Computer Architecture

Yonam Institute of Digital Technology

OverviewIntroduction of Computer

Architecture

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Computer?

What is the difference between desktop computer

and embedded computer?

Basic ConceptsBasic Concepts

What is Computer?

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Computer is a machine for

processing, storing, and retrieving data.

1) processor, memory, devices and so on.2) firmware, bootloader, operating system, application

Computer is composed of

hardware1) and software2)

Introduction of Computer Architecture

•Software Layers

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Introduction of Computer Architecture

Basic System Architecture

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Introduction of Computer Architecture

•Processor? Or Controller?1)

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ControlUnit

ArithmeticUnit

RegisterUnit

Auxiliary MemoryUnit

Main MemoryUnit

OutputUnit

InputUnit Interrupt

Handler

DMAHandler

ParallelIO Port

SerialIO Port

ROM

RAMTimer/Counter

AD/DAConverter

CPUCore

1) The figures on this slide are cited from http://sjlee.sch.ac.kr/lecture/mp/06-mp-mpintro-1.pdf

Introduction of Computer Architecture

•Data Flow (Instruction vs. Data)

CPU Memory CPU MemoryRead

Read

Write

Instructions Data

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Introduction of Computer Architecture

•von Neumann vs. Harvard

CPU

ProgramandData

Memory

von Neumann Architecture

DataMemory

CPUProgramMemory

Harvard Architecture

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Introduction of Computer Architecture

•How to Access I/O Device

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Introduction of Computer Architecture

•Bus▫A physical group of signal lines that have a

related function▫Makes it possible to transfer information from

one device to another

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3-Bus System

Introduction of Computer Architecture

•Processor Operations

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Writing data to memory and IO device Reading data from memory and IO device Reading instruction from memory Manipulating data within processor internally

Introduction of Computer Architecture

•ALU (Arithmetic Logic Unit)▫performs the mathematical operations of data

within processor addition, subtraction, NOT, AND, OR, shift,

rotate, and so on

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register

registeror

memory

registeror

memory

Introduction of Computer Architecture

Interrupt

•Interrupts (traps or exceptions)▫A technique of diverting the processor from the

execution of the current programs so that it may deal with some event that has occurred.

•Types of Interrupts▫Hardware interrupts▫Software interrupts

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Introduction of Computer Architecture

•Polling vs. Interrupt

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Start

Return

Device 0Flag set?

Device 1Flag set?

Service Device 0

Return

Return

Service Device 1

yes

yes

no

no

Introduction of Computer Architecture

•Interrupt Handling

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Introduction of Computer Architecture

CISC vs. RISCCISC1) RISC2)

# of instructions A few hundreds A few tens

Instruction Length Variable (1 ~ 17 bytes) Fixed (4 bytes)

Instruction execution time

Variable (1 ~ 300 clks / inst.)

Fixed (1 clk/inst.)

Pipelining Not efficient Efficient

# of registers Small (about 8) Large (32 ~ 200)

Data memory access Memory Operands Load, store only

Design effort 5 – 10 X 600 (m/y) 1 X 60 (m/y)

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1) CISC: Complex Instruction Set Computer2) RISC: Reduced Instruction Set Computer

Introduction of Computer Architecture

•Pipeline

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Fetch: Instruction fetch & increase PC Decode: Instruction decode & register read Execute: ALU operation or address calculation Memory: Data cache access Write: Register write-back

Introduction of Computer Architecture

Digital Signal Processor (DSP)

•Supports instruction sets and architectures optimized for numerical processing of array data.

•Extends the Harvard architecture to separate data and code spaces.

•Commonly used in embedded applications

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Introduction of Computer Architecture

MemoryMemory

Memory Organization

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Introduction of Computer Architecture

Random Access Memory: RAM•Working memory with volatility

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SRAM

StrengthsHigh Speed

DrawbacksLow Density

High CostSRAM Size of > 10MB is not practical

Used in L2 on-chip Cache & L3 off-chip

Cache

DRAM

StrengthsLow Cost

High Density

DrawbacksLow Speed

Used in Main Memory

Introduction of Computer Architecture

Read-Only Memory: ROM

• Nonvolatile memory▫ Can be read from▫ Can not be written to

• To hold the code that needs at power-up▫ Firmware, bootloader or application

• Variations▫ OTP ROM (One-Time Programmable ROM)▫ EPROM (Erasable Programmable ROM)▫ E2PROM (Electrically EPROM)▫ Flash

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Introduction of Computer Architecture

Input/OutputInput/Output

Device Communication

•I/O devices▫Used by the processor to communicate with

external world Serial: keyboard, mouse, modem, etc Parallel: disk-drive controller, video and audio

controller, …•How to exchange data

▫Programmed I/O▫Interrupt-driven I/O▫Direct Memory Access (DMA)

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Introduction of Computer Architecture

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Start

Check status of disk

Disk ready?

Send data from memory to disk or

from disk to memory

Done?

End

yes

no

yes

no

Start

Issue read or write request to disk

Do other processing until disk issues an interrupt

Transfer data between disk and memory

Done?

yes

no

End

Programmed I/O Interrupt-Driven I/O

Introduction of Computer Architecture

Direct Memory Access

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DMA types Standard block transfer Demand-mode transfer Fly-by transfer Data-chaining transfer

Introduction of Computer Architecture

Parallel andParallel andDistributedDistributedComputersComputers

Single-Instruction Multiple-Data (SIMD)

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All PEs execute synchronously the same instructions using private data Instructions are broadcast globally by a single control unit Single control thread, single programControl Unit

Processor

Memory

PE0

Processor

Memory

PE1

Processor

Memory

PE2

Processor

Memory

PEn-1

Interconnection Network

……

Introduction of Computer Architecture

Multiple-Instruction Multiple-Data (MIMD)

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Processor

Memory

PE0

Processor

Memory

PE1

Processor

Memory

PE2

Processor

Memory

PEn-1

Interconnection Network

……

Each PE executes asynchronously its own instructions using private data Multiple control thread, multiple collaborating programs

Introduction of Computer Architecture

Shared Memory Computer

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Introduction of Computer Architecture

Message-Passing Computer

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Introduction of Computer Architecture

Embedded Computer Architecture

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Block Diagram of an Generic Computer

Introduction of Computer Architecture

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Block Diagram of an Embedded Computer

Introduction of Computer Architecture