Embedded Systems Lesson 1.pdf

Embedded Systems Lesson 1 EMBEDDED SYSTEMS consists of computer hardware with embedded software which is a dedicated system for applications hardware platform with microprocessor or microcontroller and input/output devices whic...

Embedded Systems Lesson 1 EMBEDDED SYSTEMS consists of computer hardware with embedded software which is a dedicated system for applications hardware platform with microprocessor or microcontroller and input/output devices which support required tasks and implement software that perform the required processing includes programmable computer but not itself a general purpose system embedded computing system design includes: - Automobiles - smartphones - household appliances Three main components of an Embedded System: 1. hardware components - similar to computer hardware but does not require any secondary memory 2. main application software - embedded in the system, concurrently performs many tasks or processes or threads 3. real time operating system (RTOS) - embedded in a embedded system, supervises execution of application, task priorities CATEGORIES OF EMBEDDED SYSTEMS Small scale embedded systems: uses eight or sixteen bit microcontrollers simple and may be battery operated editor, assembler and cross assemblers are used for software if C language is used for programs, executable codes are stored in the system memory memory capacity should be sufficient to store the software Medium scale embedded systems: sixteen or thirty two bit microcontrollers are used may also employ the readily available single purpose processor Hardware and software is complex programming tools are object oriented programming, RTOS, simulator, debugger etc  Sophisticated embedded systems: require Intellectual Property (IPs) core, scalable processors, configurable processors and Programmable Logic Arrays (PLA) IP provides a design for implementing Hyper Text Transfer protocol (HTTP) or File Transfer Protocol (FTP) or Bluetooth protocol to transmit file on internet used for cutting edge applications which require hardware and software co-design software implements some of the functions of the hardware resources. Requirement of Embedded Systems embedded computing is much more demanding than the programs written for PCs or workstations embedded applications must meet many constraints Embedded computing systems have to provide sophisticated functionality: - Complex algorithms: operations performed may be very sophisticated - User interface: complex user interfaces that may include multiple menus and many options - Real time: data is not ready by a certain deadline, the system breaks - Multirate: several real-time activities going on at the same time, may simultaneously control some operations that run at slow rates and others run at high rates (eg Multimedia applications)  Non-functional requirements: - Performance - Cost - Physical size and weight - Power consumption Functional requirements: - Proper hardware - Minimum power consumption - Consideration of upgradeable design - Complex method of testing - Limited observability and controllability; Constraints Processor speed System memory Power dissipation in run, wait for events, wake-up, sleep and stop cycles EMBEDDED PROCESSORS a programmable logic device which can be used as processing unit or computing unit has decision making capability by executing a program logical circuits of microprocessors are operated by binary numbers 0 or 1 called machine language machine language is tedious, instructions are abbreviated to write the program in an easy way called mnemonics language developed by mnemonics is called assembly language set of instructions written for the microprocessor to accomplish a task is called program and a group of programs is called software microprocessor is manufactured by very large-scale integration (VLSI) technology it is a clock driven semiconductor device consists of following three building blocks - Register array - consist of memory elements - Arithmetic and logic Unit (ALU) - used for mathematical computation and logical decision - Control unit (CU) - controls the operation of microprocessor by providing control signals, also controls the timing of operation of different circuits in the microprocessor  Integrated Circuit technology integration development: 1. Small-Scale Integration (SSI): less than one hundred components, used for fabrication of logic gates 2. Medium-Scale Integration (MSI): less than one thousand but more than one hundred gates, used for fabrication of hundreds of logic gates in IC 3. Large-Scale Integration (LSI): less than ten thousand but more than one thousand logic gates is called large-scale integration or LSI, used for fabrication of INTEL 4004 microprocessor 4. Very Large-Scale Integration (VLSI): designed with more than ten thousand logic gates, used for fabrication of INTEL 8085 5. Super Large-Scale Integration (SLSI): designed with more thana million logic gates, used for fabrication of advanced microprocessors INTEL Early Microprocessors, a brief history first microprocessor was developed in 1971 in the brand name of INTEL 4004 a 4 bit microprocessor designed with large scale integration (LSI) technology number of instruction was 45 and fabricated by PMOS technology  rate of execution of the instructions by this microprocessor is 50 KIPS (Kilo instruction per second) 1972, first 8 bit microprocessor INTEL 8008, can address an expanded memory size of 16 Kilobytes and 48 instructions 1973, first modern 8 bit microprocessor INTEL 8080, fabricated by NMOS technology ten times faster than 8008 microprocessor, 500 KIPS execution rate memory capacity is 64 KB, four times more than that of 8080 1975, improved version of 8 bit microprocessor INTEL 8085 769.23 KIPS, own internal clock generator and system controller, 246 instructions 1 - Intel 4004  2 - Intel 8080 3 - Intel 8085 1978, 16 bit microprocessor INTEL 8086 after one year, released INTEL 8088 can address one Megabyte of memory location and execution speed is 2.5 MIPs speed of execution is increased by using instruction queue or cache, pre-fetch few instructions and place them in queue before execution instruction sets are large in number and complex in operation, complex instruction set computers(CISC) have more internal registers to provide more storage space than that of 8085,16 bit registers help to write program efficiently complexity of instructions of CISC microprocessor causes reduction in computing speed  reduced instruction set computer (RISC) microprocessor is developed to increase computing speed by decreasing execution time using hardwired control unit 4 - Intel 8086 Microprocessor functional units 1. Bus Interface unit (BIU) - also called as program flow control unit, performs the following functions a. transmits address of instruction and data b. fetches instructions from memory c. reads data from input/output ports and memory d. writes data to input output/ports and memory  e. performs the function of all data and address transmission through the buses for execution unit f. generates 20 bit address using 16 bit offset address and content of segment registers 2. Execution unit (EU) - sends signal to BIU to fetch instruction or data, decodes and executes instructions, the Arithmetic and Logic Unit (ALU) Processor selection considerations: 1. Maximum bits in the operand 2. Instruction set 3. Clock frequency 4. ability to solve complex algorithms Advantages of Microprocessor for Embedded Systems: 1. System development is easy 2. I/O interfacing can be used for new system 3. Compiler facilities in high level language are available 4. Tested and debugged processor specific Application Program Interfaces (APIs) are available Microcontroller  a general purpose microprocessor with built-in RAM, ROM, I/O ports, and timers all on a single chip used to read data, perform limited calculations and control the interfaced devices based on those calculations, stores the program in ROM Microcontroller additional circuits: 1. Analog to Digital Converters (ADC)- convert external signals to digital signals 2. Counter arrays - counter circuits for pulse generation 3. Watchdog Timers (WDT) - used to reset the microcontroller if program execution hangs-up 4. Pulse Width Modulation (PWM) circuit - speed control of DC Motors 5. Universal Synchronous and Asynchronous Receiver Transmitter (USART) - used for serial data transfer 6. Phase Locked Loop (PLL) circuit - used for synchronous communication 7. External bus controllers -used for controlling the bus system to connect static (RAM/ROM) and dynamic (SDRAM) Microcontroller types based on Bits Four bit microcontrollers, low cost microcontrollers used in electronic toys and in alphanumeric LED/LCD display drivers and portable battery chargers Eight bit microcontrollers, most popular microcontroller in use, suitable for word size controller tasks. 1 byte is adequate for most of the control and monitoring application and data communication  used in various control applications such as speed control of electric motors, position control and process control system Sixteen bit microcontrollers, can be programmed using high level language as well as assembly level language used in disc drives, modems, printers, scanners, servo control systems Thirty two bit microcontrollers, are used for very high speed intelligent control systems and image processing, can be programmed in both high level and assembly,