Embedded Systems Computer Organization Wednesday 25 November 15
Summary Previous Class Analog-Digital Interface Today: Embedded Systems Characteristics Architectures Complete Systems Computer Organization 2
Embedded Systems What is an embedded system? Not always easy to define: Any sort of device which includes a programmable computer but itself is not intended to be a general-purpose computer An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system. A specialized computer system that is part of a larger system or machine An embedded system is a computer that has been built to solve only a few very specific problems and is not easily changed An embedded system is some combination of computer hardware and software, either fixed in capability or programmable An embedded system contains a computer as part of a larger system and does not exist primarily to provide standard computing services to a user Keywords: variety, combination, any sort, dedicated, Computer Organization 3
Growing Market Smart homes Internet of Things (IoT) Vehicle networks Wearables Healthcare Security Embedded Systems Main goals Reliable Energy efficient Low energy, or energy harvesting Cheap Customizable and adaptable adapt to the user s specific needs and evolve with the market Computer Organization 4
Application Examples Personal appliances Cellular phones Watches Smart watches Calculators Home appliances Alarms Thermostats Air conditioners Remote controllers Most domestic machines Computer components Mouse Keyboards Routers Battery charger 3D Printers Computer Organization 5
Application Examples Car industry On-board computer Controllers of traction, injection, transmission, break (ABS), etc Air bag Air conditioning Instrumentation Industrial applications Industrial robots (manipulators) Belt conveyor systems Lifts Automatic control Instrumentation Entertainment Video games Consoles Toys Computer Organization 6
Automotive Embedded Systems Today s high-end automobile have more than 100 microprocessors: 4-bit microcontroller checks seat belt microcontrollers run dashboard devices 16/32-bit microprocessor controls engine Customer s requirements Reduced cost Increased functionality Improved performance Increased overall dependability Computer Organization 7
An Engineering View Computer Organization 8
Real Time Systems Real time systems have to guarantee that they will respond to an external event within a specified amount of time. Do not have to be fast, but have to be reliably on time. System design: Interrupt handling has to be specially careful. Since task scheduling and interrupt handling is performed by the operating system, real time must be supported by the OS (RTOS). Soft real time is usually available (linux, windows), but not hard real time... Computer Organization 9
Real Time Systems Real time systems are classified as: soft real time provide a statistical time guarantee. Missing an event is not catastrophic. e.g. TV screen. If a glitch is visible it is not catastrophic. hard real time Time guarantee is absolute. Missing a timing deadline will lead to catastrophic results. e.g. Brake sytem of a car. If an event is delayed it may be catastrophic. Soft and hard real time? soft real time systems are optimized for the average case More relaxed designed, cheaper, and easier to design hard real time systems must guarantee worst case situations, always. Strict design, strict time Computer Organization 10
Power and Energy Power and Energy Energy provides the ability to work Power is the amount of energy over an amount of time Watts = Joules / second Battery provides finite amount of energy and power (i.e. depend on the maximum current that it can output) In mobile systems we mainly care about energy Budget energy to prolong battery life Computer Organization 11
Power and Energy Reduction Main power drain sources Computation Wireless transmission Sensors and actuators Memory How to reduce power consumption Circuit level Computational architecture, frequency and voltage reduction, turn off circuits, asynchronous circuits, different technologies, Usually out of our control System level Code, compiler, and OS energy awareness Scheduling, optimize memory access, reduce pipeline stalls, context switching, turning off when idle Computer Organization 12
Watchdog Timer Watchdog timer Hardware timing device that triggers interruption for system reset, alarm management, or similar operation after a predefined amount of time Can be a stand-alone hardware component or built into the processor itself. Allows for the systems to be put to sleep until next time event embedded system software are many times in the form of endless loops. for(;;) { } function(); sleep(); Computer Organization 13
Interface with the User Keyboard Embedded system composed by a built-in microcontroller to read the pressed keys; Communicates with the PC using USB. Mouse The whole keyboard is read by repetitively testing all lines, with a fast frequency (e.g.: 50Hz). The light emitted by a LED/laser is reflected on the table surface and acquired by a small camera The small (simple) camera acquires about 1500 images per second The controller circuit detects the pattern differences and determines the movement direction Computer Organization 14
Touch-Screen Displays Most common technologies: Resistive; Cheaper Very resistant and durable Very good resolution; Not affected by cloths, such as gloves Capacitive; Little visibility loss; Not affected by dirt, fat or humidity. Computer Organization 15
Microprocessor Varieties Processing unit particularly suited to the control of simple procedures or devices in embedded systems Processor families: General Purpose Processors (GPP) transfer and data manipulation operations (MOVs); conditional execution operations (IF... ELSE...) Digital Signal Processors (DSP) microprocessor optimized for digital signal processing Mathematical computation (mainly, multiplications) Microcontrollers includes on-board memory and I/O devices (peripherals) to interface with the outside world Common applications: control, actuators, instrumentation, etc Computer Organization 16
GPPs versus Microcontrollers General Purpose Processors (GPPs) CPU, Memory and IO integrated on a set of chips, on a board or several boards Microcontrollers CPU, Memory, IO and peripherals integrated in a single chip Computer Organization 17
GPPs versus Microcontrollers General Purpose Processors (GPPs): High performance CPU, in an independent chip Absence of any RAM, ROM and IO modules in the CPU chip The used memory space should be defined and adjusted according to each particular application Peripherals (timer, serial port, etc.) are external to the CPU chip Expansible, versatile and general purpose Computer Organization 18
GPPs versus Microcontrollers Microcontrollers: CPU with few resources (e.g.: 8-bits) RAM, ROM and IO integrated within the CPU chip The available memory space is fixed Peripherals integrated within the CPU chip. Suitable for low-cost and constrained (power, HW, etc.) applications Computer Organization 19
Microcontroller s CPU and Peripherals Simple CPU, implemented with: Single-cycle state machine Control unit with a state machine Micro-programmed control unit Very simple pipeline On-chip peripherals: I/O ports RAM and ROM memories Timer Interrupt controller USART Parallel port; etc. Computer Organization 20
Microcontrollers Families Most manufacturers offer a wide set of devices, with different performance levels Processing power: 4-bits, 8-bits, 16-bits, 32-bits 8-bits microcontrollers are the most widely adopted and used by the majority of the applications 32-bits and 64-bits are only requested by very specialized and reduced markets, with very specific requisites: Communications Signal processing Video processing etc. Computer Organization 21
Microcontrollers Families Atmel AVR ARM Intel 8-bit 8XC42 MCS48 MCS51 8xC251 16-bit MCS96 MXS296 Microchip 12-bit instruction PIC PIC12F508 14-bit instruction PIC PIC16F84 16-bit instruction PIC National Semiconductor COP8 NEC Motorola 8-bit 68HC05 68HC08 68HC11 16-bit 68HC12 68HC16 32-bit 683xx SGS/Thomson ST62 Texas Instruments TMS370 MSP430 Zilog Z8 Z86E02 Computer Organization 22
Market: Microcontrollers Market 8 and 16-bit microcontrollers satisfy more than 75% of the market needs! Dominant microcontrollers: Microchip 16Fxx Intel 8051 and derivatives Motorola MC68HC05 Computer Organization 23
Microcontroller Packaging and Appearance From left to right: PIC 12F508, PIC 16F84A, PIC 16C72, Motorola 68HC05B16, PIC 16F877, Motorola 68000 Computer Organization 24
Example: Microchip Microcontrollers PIC Family Large microcontrollers (PIC) family Advanced communication peripherals and protocols Wide processing capacity offer 8, 16 or 32 bits Several (memory) addressing spaces available: RAM ROM EEPROM Flash Computer Organization 25
Example: Microchip Microcontrollers PIC Family Vast set of peripherals and protocols: Communication peripherals and protocols: RS232/RS485 SPI I2C CAN USB TCP/IP Ethernet Control and timer peripherals: Acquisition and comparison Pulse Width Modulation (PWM) Counters and timers Watchdogs Visual peripherals: LED drivers LCD drivers Analog peripherals: A/D converters up to 12- bits D/A converters Comparators and signal amplifiers Voltage detectors Temperature sensors Oscillators Voltage references Voltage regulators Computer Organization 26
Example: Microchip Microcontrollers PIC Family Computer Organization 27
Single Board Computers F77B MINI2440 + 7 ' 150 (2015) ARM9 400 MHz Samsung S3C2440A ARM920T RAM 64 MB sdram 32 bits Bus Flash 64 MB - 1 GB I/O: Ethernet 7 touch screen SD-Card slot 3,5 mm Stereo Jack USB OS support Windows CE 5 e 6 Linux 2,6 Android Many others: raspberry pi, Intel NUC, Computer Organization 28
Smart-Cards Appeared in the beginning of the 1970 s, but... Only by the beginning of the 1980 s were the supporting technologies developed Two types of cards: Memory card (without CPU) Card with microprocessor Chip Plastic card Computer Organization 29
Smart-Cards Applications Information technology Secure access and user authentication Storage of digital certificates and passwords Encryption of critical data Cellular phones (GSM) Subscriber authentication Data storage e-commerce e-banking and e-payments Identification and access control (tickets) Parking Phone credit (decrement of a credit counter) Computer Organization 30
Smart-Cards Smart-Cards with microprocessor Processor Usually, 16-bits @ 5-16 MHz Cryptographic co-processors Memory ROM (16 kbytes - 128 kbytes) for the operating system EEPROM (4 kbytes - 64 kbytes) for persistent data RAM (256 Bytes 4k Bytes) for data ROM size 4 EEPROM size 16 RAM size File system supported on the installed memory Small silicon area (5mm 2 ), due to space and energy restrictions Computer Organization 31
Smart-Cards Communication Contact-based Contact-less (transmission with an antenna) Serial protocol, 9600 bps Power-supply With battery Without battery the CPU is powered with an inductive circuit Computer Organization 32
Smart-Cards: Infineon SLE66 Computer Organization 33
Conclusion Microprocessors come in many varieties GPP DSP Microcontrollers Smartcards A significant share of the market is targeted to embedded systems: I/O Small Cheap Application oriented Energy restricted Computer Organization 34
Next Class Multiprocessors Programming overheads Shared-Memory Multiprocessor UMA vs NUMA Memory coherence Computer Organization 35
Embedded Systems Computer Organization Wednesday 25 November 15
Interface with the user LCD Display Touch-Screen Displays Computer Organization 37
GPPs versus Microcontrollers Adopted architectures: Von Neumann architecture: Single memory shared by program and data The processor is interconnected by a data and an address bus Harvard architecture: Separated memories for program and data Independent data and address buses for each memory device Computer Organization 38
Smart-Cards: Dallas ibutton Applications: Access control; Each unit has an unique address; Interface: Only two wires: Power + Data Ground Serial communication: 16kbps to 142kbps Available models: Address-only (ID only); Memory-only; Real-time clock; Authentication/encryption key; Sensor (thermometer, hydrometer); Data-logger. Computer Organization 39
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Example: Intel MCS-51 Microcontrollers Family 8-bits microcontroller Introduced in the market by Intel (8051) by the end of the 1970 s One of the most popular microcontrollers (about 40% of the market) Today, it is produced by several manufacturers in different formats: Intel 8751 microcontroller UV-EPROM Philips 8051 AD, DA, extended I/O, and flash Atmel AT89C51, Flash (erase before write) Dallas Semiconductor DS5000 NV-RAM, RTC Computer Organization 41
Example: Intel MCS-51 Microcontrollers Family Intel MCS-51 Family: CPU, RAM, ROM, I/O, interrupt logic, timer, etc. in a single chip 8-bits data bus 16-bits address bus can access 2 16 = 64 kb memory positions (RAM and ROM) On-chip RAM: 128 bytes ( Data Memory ) On-chip ROM: 4 kb ( Program Memory ) 4-bytes bi-directional IO port UART (serial port) 2 16-bit counters/timers Interrupt controller (2 priority levels) Low-power mode Computer Organization 42
Example: Intel MCS-51 Microcontrollers Family Architecture: Computer Organization 43
Example: Intel MCS-51 Microcontrollers Family Internal peripherals: Parallel IO ports Clock generator Serial port Timers Interrupt controller Computer Organization 44
Example: Intel MCS-51 Microcontrollers Family Parallel IO ports: Each port can be configured either for input or output The direction is defined by special registers Serial port: Data is sent/received serially The transmission rate (BAUD rate) and the transmission mode are configured with specific registers (SFR) Computer Organization 45
Example: Intel MCS-51 Microcontrollers Family 2 internal timer: Each timer increments the counter at each clock cycle The count limit is configured using specific timer registers (TH0, TL0, TH1, TL1) The current count value can be read in registers TH0, TL0, TH1, TL1 At the end of the count: An interruption is generated Dedicated bits at SFR register are activated Computer Organization 46
Example: Intel MCS-51 Microcontrollers Family Interrupt controller 5 types of interruption: Timer 1 Overflow Timer 2 Overflow External interruption 1 External interruption 2 Serial port event (buffer full, buffer empty, etc.) Interruptions are activated/inhibited using the SFR register. Computer Organization 47
Example: Microchip Microcontrollers PIC Family PIC Family Stack Size Instruction Word Size No of Instructions Interrupt Vectors 12CX/12FX 2 12- or 14-bit 33 None 16C5X/16F5X 2 12-bit 33 None 16CX/16FX 8 14-bit 35 1 17CX 16 16-bit 58 4 18CX/18FX 32 16-bit 75 2 Computer Organization 48
Example: TMS32010 Computer Organization 49
Example: Philips TriMedia-Processor Computer Organization 50
Example: SH-MobileG1 chip System on a Chip (SoC) Computer Organization 51
Smart-Cards Dedicated commands to support secure / cryptography protocols Access control Examples: check key(), change key() Authentication Examples: authenticate() Encryption Examples: start encryption(), stop encryption() Atomic operations Examples: exchange(), increment(), decrement() Computer Organization 52