Designing Embedded Hardware 01. Introduction of Computer Architecture Yonam Institute of Digital Technology

Overview Introduction of Computer Architecture 2 Computer? What is the difference between desktop computer and embedded computer?

Basic Concepts

What is Computer? 4 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 hardware 1) and software 2) Introduction of Computer Architecture

Software Layers 5 Introduction of Computer Architecture

Basic System Architecture 6 Introduction of Computer Architecture

Processor? Or Controller? 1) 7 Control Unit Arithmetic Unit Register Unit Auxiliary Memory Unit Main Memory Unit Output Unit Input Unit Interrupt Handler DMA Handler Parallel IO Port Serial IO Port ROM RAM Timer/ Counter AD/DA Converter CPU Core 1)The figures on this slide are cited from Introduction of Computer Architecture

Data Flow (Instruction vs. Data) CPU Memory CPU Memory Read Write InstructionsData 8 Introduction of Computer Architecture

von Neumann vs. Harvard CPU Program and Data Memory von Neumann Architecture Data Memory CPU Program Memory Harvard Architecture 9 Introduction of Computer Architecture

How to Access I/O Device 10 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 11 3-Bus System Introduction of Computer Architecture

Processor Operations 12  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 13 register or memory register or 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 14 Introduction of Computer Architecture

Polling vs. Interrupt 15 Start Return Device 0 Flag set? Device 1 Flag set? Service Device 0 Return Service Device 1 yes no Introduction of Computer Architecture

Interrupt Handling 16 Introduction of Computer Architecture

CISC vs. RISC CISC 1) RISC 2) # of instructionsA few hundredsA few tens Instruction LengthVariable (1 ~ 17 bytes)Fixed (4 bytes) Instruction execution timeVariable (1 ~ 300 clks / inst.)Fixed (1 clk/inst.) PipeliningNot efficientEfficient # of registersSmall (about 8)Large (32 ~ 200) Data memory accessMemory OperandsLoad, store only Design effort5 – 10 X 600 (m/y)1 X 60 (m/y) 17 1)CISC: Complex Instruction Set Computer 2)RISC: Reduced Instruction Set Computer Introduction of Computer Architecture

Pipeline 18  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 19 Introduction of Computer Architecture

Memory

Memory Organization 21 Introduction of Computer Architecture

Random Access Memory: RAM Working memory with volatility 22 SRAM Strengths High Speed Drawbacks Low Density High Cost SRAM Size of > 10MB is not practical Used in L2 on-chip Cache & L3 off-chip Cache DRAM Strengths Low Cost High Density Drawbacks Low 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 23 Introduction of Computer Architecture

Input/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) 25 Introduction of Computer Architecture

26 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/OInterrupt-Driven I/O Introduction of Computer Architecture

Direct Memory Access 27 DMA types  Standard block transfer  Demand-mode transfer  Fly-by transfer  Data-chaining transfer Introduction of Computer Architecture

Parallel and DistributedComputers

Single-Instruction Multiple-Data (SIMD) 29  All PEs execute synchronously the same instructions using private data  Instructions are broadcast globally by a single control unit  Single control thread, single program Control 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) 30 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 31 Introduction of Computer Architecture

Message-Passing Computer 32 Introduction of Computer Architecture

Embedded Computer Architecture 33 Block Diagram of an Generic Computer Introduction of Computer Architecture

34 Block Diagram of an Embedded Computer Introduction of Computer Architecture