Components of Embedded Systems
Embedded Systems Processors
Microprocessors (μP)
•High Flexibility, Frequent Configuration Upgrades •No Power, Area and Integration Constraints Microcontrollers (μC) •High Integration, Power Saving highly desirable •Limited Configurability, Static & Fixed Design •Area constraints are prominent Digital Signal Processors (DSP) •Signal, Speech, Image Processing Applications •Need for Multiply-Add-Accumulate functionality •Power, Area, Integration Constraints not dominant Digital Signal Controllers (DSC) •Signal, Speech, Image Processing Applications •Need for Multiply-Add-Accumulate functionality •Stringent Power, Area, Integration Constraints System On Chip (SOC) •Very high integration with OS environment needed •Power, Area constraints are to be met •High end software application is executing Application Specific Integrated Circuits (ASIC) •High integration with fixed task operation •Application specific logic consumes larger chip area •Power, Area, Integration Constraints are dominant |
Embedded Systems memories
Static RAM (SRAM)
•High Speed, No refreshing required •Low packing density, High Cost / Unit •High Current / Power consumption, heat dissipation Dynamic RAM (DRAM) •Moderate Speed, Refreshing & Recharging required •Very high packing density, Low Cost / Unit •Low Current / Power consumption, heat dissipation Non-Volatile RAM (NVRAM) •Moderate/Low Speed •Retains Data contents when power is turned off Static RAM (SRAM) •Used when High speed, small sized memories are required •Cache, Buffers, Video Buffers Dynamic RAM (DRAM) •Used when Large sized (Bulk) memories are needed and speed constraint is not stringent. •Main Memory Non-Volatile RAM (NVRAM) •Used when non-volatile storage is necessary •Configuration Memory, Setup / Table storage One Time Programmable ROM (OTPROM) •Based on Fused Gates – Fuse blown turns 1 to 0 •Moderate Speed, writes only once. •Retains data permanently •Used for Master Programs / Data permanent storage Read Only (mask) Memory (ROM) •Locations are stored permanently by appropriate VLSI Mask •Moderate Speed, Not user writable •Retains data permanently •Used for absolute static data – Character generators Erasable Programmable ROM (EPROM) •Based on Floating (Charge) Gates •Erased by UV light, Programmed by High Voltage (12/30V) •Sustains 1000 Write cycles, retains data for 100 years •Used for general purpose – BIOS, Boot / control programs Electrically Erasable Programmable ROM (EEPROM) •Based on MOS gates – Non-volatile characteristics •Very Slow Speed •Writes/programs Location-wise •Sustains 100,000 write cycles , Retains data for 10 years •Used for Configuration / parameter / set up storage Flash Programmable ROM (Flash) •Based on technology same as that of EEPROM •Good speed, very good packing density •Writes/programs Sector-wise •Sustains 100,000 write cycles , Retains data for 10 years •Used for general purpose, program memory, data memory, solid state drives, USB drives, most commonly used currently. |
Input Devices
Character Input Devices •Keyboards •Keypads, Number-pads Pointing Devices •Mouse, Trackball •Joystick, Track-point •Touch-pad, Touch-screen Image Capture Devices 1-Dimensional CCD Sensors (Strip) •Hand held Scanners / Flat bed scanners Bar Code scanners •2-Dimensional CCD Sensors (Matrix) •CCD Camera, CCTV Camera •Digital-Cam, Handy-Cam, Web-Cam Output Devices Display Devices •CRT Displays •Raw CRT Screens •CRT SVGA Monitors •LCD Displays •LCD Numeric / Calculator Displays •LCD Alphanumeric Displays •LCD Graphic Displays •LCD 64K Mobile / PDA Displays (Passive Matrix) •LCD SVGA Monitors (Active Matrix / TFT XGA) •LEDs / LED Displays •Discrete LEDs / Multicolor LEDs / RGB LED •LED Clusters •LED 7-Segment Numeric Displays •LED Alphanumeric / Multi-segment Displays •LED Screen Displays •LED Monitors (SVGA compatible) •LED 3D / HD Monitors (SVGA compatible) Printers Speakers |