Microprocessor and Programmable Logic Control (PLC)

1
Microprocessor and Programmable Logic Control
(PLC)
2
Microprocessors

• Informally, a microprocessor (µP) is the brain
  of a computer that has been implemented on one
  semiconductor chip.
• More precisely, a microprocessor is a single-chip
  central processing unit (CPU) for a programmable
  computer.
• A CPU may be considered to be the brain of a
  computer because it understands and executes
  the sequence of binary instructions in a compiled
  computer program.
• Compared to the CPU, the other parts of a
  computer are relatively dumb and require
  detailed attention from the CPU in order to
  function properly in the computer system.

3
Applications of Microprocessors

• Microprocessors can be found just about
  everywhere
• In general-purpose computers, like mainframes,
  personal computers (PCs), and single-board
  computers (SBCs).
• In special-purpose computers, like calculators,
  personal data assistants (PDAs), and game
  computers.
• In embedded computers that control automobiles,
  appliances, instruments, communication systems,
  cell phones, factories, assembly lines,
  refineries and etc.
• Ex. In a car Microprocessors are used in the
  ignition system, emission control system,
  anti-lock brakes, dashboard display,
  entertainment system, navigation system, etc.
  Modern cars often contain 20 or more
  microprocessors.

4
Microprocessors History

• The microprocessor became possible only after
  integrated circuit technology had advanced to the
  point where several thousand transistor switches
  could be integrated onto a single semiconductor
  chip.
• The Intel 4004 (1971) was the first
  microprocessor
• originally developed for a desktop calculator
  product
• contained 2300 transistors
• occupied a silicon area of 12 mm2
• implemented in 10 µm PMOS semiconductor
  technology
• data bus was 4 bits wide
• 640 bytes of data could be addressed
• system clock run at a frequency of 108 KHz
• could perform roughly 60000 operations per second

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Microprocessors History (cont.)
Intel 4004 Was Intel's first microprocessor. It
contained 2,300 transistors and was built using a
10 micron process. It had a total of 16 pins.
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Microprocessors History (cont.)

• The Intel Itanium entered mass production in
  2001
• intended for high-end servers and workstations
• contains 25.4 million transistors
• silicon chip area exceeds 300 mm2
• 180 nm CMOS semiconductor technology
• 6 layers of metal interconnections
• 1012 chip pad connections
• 64-bit data bus 64-bit address bus 64-bit
  registers
• memory space of over 18 terabytes (264 18.45 x
  1018).
• system clock frequency of at least 800 MHz
• peak performance of 3.2 billion instructions per
  second
• The pace of technological progress shows no signs
  of slowing down in the immediate years ahead . . .

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Microprocessors History (cont.)
Pentium 4 42 million transistors and circuit
lines of 0.18 microns. Intel's first
microprocessor, the 4004, ran at 108
kilohertz (108,000 hertz), compared to the
Pentium 4 processor's initial speed of 1.5
gigahertz (1.5 billion hertz).
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Microprocessors Revolution

• The appearance of the microprocessor
  revolutionized digital system design starting in
  the 1970s, and continuing on until the present
  day.
• The main advantages of the microprocessor
• Programmability Sophisticated functions can be
  provided relatively easily in software.
• Performance Advances in integrated circuit
  technology are leading to faster and more
  powerful microprocessors.
• Cost-effectiveness Microprocessors, because they
  are multi-purpose, are manufactured in large
  quantities, which tends to minimize their unit
  cost.
• Reliability Integrated circuits are
  highly-reliable, solid state devices.
  Microprocessors have no moving parts.
• Compactness More and more functionality can be
  packed onto a single microprocessor/microcontrolle
  r chip.

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Basic Microprocessors System
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Basic Microprocessors System (cont.)

• A basic microprocessor system consists of the
  microprocessor core, memory, input/output
  modules, and a system bus connecting these
  modules.
• The memory system usually consists of Read Only
  Memory (ROM) for boot information, and Random
  Access Memory (RAM) organized in a hierarchy of
  main memory and multilevel cache memory.
• Typically, the cache memory is implemented as
  level 1 cache closely coupled to the
  microprocessor core, and level 2 cache accessible
  over the system bus.
• The main memory, typically DDR SDRAM, is
  accessible over the system bus as well, but level
  2 cache (embedded SRAM) offers higher access
  speed.

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Basic Microprocessors System (cont.)

• The microprocessor core contains a datapath
  section (ALU and registers), a control section,
  and cache memory.
• Memory access rate varies according to the memory
  hierarchy from 1 cycle access rate to registers
  and level 1 cache, to 10 cycles access rate to
  level 2 cache, up to 50 cycles access rate to
  main memory.
• These are typical values and may vary from system
  to system.

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Type Of Microprocessors

• Computers based on a CPU with a complex
  instruction set known as CISC (Complex
  Instruction Set Computer) microprocessor
• Intel
• A RISC (Reduced Instruction Set Computer) has
  limited set of instructions that it can perform
  quickly
• AMD

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The Embedded Processor

• A programmable processor whose programming
  interface is not accessible to the end-user of
  the product.
• The only user-interaction is through the actual
  application.
• Examples
• Sharp PDAs are encapsulated products with fixed
  functionality.
• 3COM Palm pilots were originally intended as
  embedded systems. Opening up the programmers
  interface turned them into more generic computer
  systems.

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Disadvantages of Microprocessors

• Microprocessors have many complex features.
  Numerous features are provided to satisfy a wide
  variety of users.
• Microprocessors are completely unforgiving when
  program errors are made. They will execute
  exactly what is in the program, and have no
  common sense or intuition about what the
  designer intended the program to do.
• Debugging tools for microprocessor assembly
  language programs are usually primitive compared
  to the tools available for programs in high-level
  languages.

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Microprocessors Related Terms

• A microcomputer is a computer system that has
  been built around a microprocessor chip.
• A microcontroller is an integrated circuit that
  contains a microprocessor as well as other useful
  support circuits, such at timers, memory,
  input/output interface circuits, etc.
• The EE380 lab microcomputer system contains the
  Motorola MC68332 microcontroller chip.
• A digital signal processor (DSP) is a
  specialized microprocessor that has features
  (e.g. instructions, registers, internal signal
  paths, arithmetic circuits) that make it
  particularly efficient at performing the kinds of
  numerically intensive calculations that are
  required in digital signal processing (e.g. in
  modems and cell phones)

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Microprocessors Families

• Microprocessor manufacturers tend to release
  microprocessors in families of increasing
  complexity and performance
• Intel Corp.
• 4004 (1971), 8008 (72), 8080 (74)
• x86 family 8086 (78), 8088 (79), 80186 (82),
  80286 (82), 80386 (85), 80486 (89), Pentium
  (93), Pentium II (97), Pentium III (99),
  Pentium 4 (2000), Xeon (2001)
• IA-64 family Itanium (2000),
• Motorola, Inc.
• 6800 family 6800 (1974), 6809 (79), 68HC11
  (84)
• M68000 family 68000 (1979), 68010 (82), 68020
  (84), 68030 (87), 68040 (89), 68332 (89),
  Power PC
• Microprocessor families make it easier to carry
  software over from an older µP to the latest µP.
  Upward compatibility is an important strategy
  for building customer loyalty.

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What is the next wave?
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Programmable Logic Controller

• A programmable logic controller (PLC) is a solid-
  state device designed to perform logic functions
  previously accomplished by electromechanical
  relays .
• The PLC is an assembly of solid-state digital
  logic elements designed to make logical decisions
  and provide outputs.
• It used for control and operation of
  manufacturing process equipment and machinery

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Programmable Logic Controller

• It has been designed to operate in the industrial
  environment and is equipped with special
  input/output interfaces and a control programming
  language
• It is capable not only performing relay switching
  tasks, but also counting, calculating, comparing
  and the processing the analog signals.

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Advantages of PLC compared with Relay

• Its eliminated much of the hand wiring
  associated with conventional relay control
  circuit.
• Its small and inexpensive compared to equivalent
  relay-based process control systems.
• Capable of simulating a hundred relay, timers and
  counters.
• Easy to program and install
• Hardware features such as keylocks can restrict
  the access to PLC, and software features such as
  passwords.
• It does can be designed with communications
  capabilities that allow them to converse with
  other computer systems or to provide human
  interfaces.

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Part of PLC
PLC Diagram
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Part of PLC (cont.)

• PLC can be divided into parts
• The central processing unit (CPU)
• The input/out (I/O) section
• The power supply
• The programming device.

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Part of PLC (cont.)

• CPU - is the brain of the PLC.
• It consists of a microprocessor for implementing
  the logic and controlling the communications
  among the modules.
• Required memory for storing the results of the
  logical operation performed by the
  microprocessor.
• The CPU is designed so that the user can enter
  the desired circuit in ladder logic.
• Power Supply used to supplies dc power to other
  modules that plug in rack and other field devices

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Part of PLC (cont.)

• Memory Module used to control input and output
  of the process.
• Programming Device - are used to enter the
  desired program into the memory of the processor.
  
• This program is entered using relay ladder logic.
  The program determines the sequence of operation
  and ultimate control of the equipment or
  machinery.

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Part of PLC (cont.)
Hand-held with LED display
Industrial terminal
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PLC Software

• Software written and run on PC has changed how
  people work with PLCs. PLC software run on a PLC
  falls into the following two categories
• PLC software that allows the user to program and
  gives the user the tools to write a PLC program
  using ladder logic or other programming language
  and document or explain the program is as much
  detail as is necessary.
• PLC software that allows the user to monitor and
  control the process is also called man-machine,
  or operator, interface. It enables the user to
  view a process or graphical representation of a
  process on a CRT, determine how the system is
  running, trend values, and receives alarm
  conditions.

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PLC PROGRAMMING LANGUAGES

• PLC programming language refers to the method by
  which user communicates information to the PLC.
• There are three most common languages
• Ladder diagram language
• The most common used by PLC language.
• Boolean language
• The statements refers to the basic AND, OR and
  NOT logic gate function.
• Function chart system
• It is a method of programming a control system
  that uses a more structured approach.

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PLC Size

• PLCs are divided into three major size
  categories
• Small It covers units up to 128 I/Os and
  memories up to 2Kb. It capable of providing
  simple to advanced levels of machine control.
• Medium It have up to 2048 I/Os and memories up
  to 32Kb. Special I/Os modules make medium PLCs
  adaptable to temperature, pressure, flow, weight,
  position and any type of analog function
  encountered in process control applications.
• Large The most sophisticated units of PLCs
  family. They have up to 16,000 I/Os and memories
  up to 2Mb. It has almost unlimited applications
  and can control individual production processes
  or entire plants.

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PLC Applications

• There are three major types of PLC applications
• Single-ended It involves one PLC controlling one
  process. This would be a stand-alone unit and
  would not be used for communicating with other
  computers or PLCs.
• Multitask It usually calls for a medium size PLC
  and involves one PLC controlling several
  processes. It can be a subsystem for larger
  processes and communicating with a central PLC.
• Control management It involves one PLC
  controlling several others. It requires a large
  PLC processor designed to communicate with other
  PLCs and possibly with a computer. The control
  management PLC supervises several PLCs by
  downloading programs that tell the other PLCs
  what has to be done.

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PLC vs Computer

• Some important characteristics distinguish PLCs
  from general-purpose computers.
• The PLC is designed to operate in the industrial
  environment with the wide range of ambient
  temperature and humidity.
• A well designed PLC is not affected by the
  electrical noise inherent in most industrial
  locations
• Hardware and software of PLCs are designed for
  easy use by plant electricians and technicians
• Unlike the computer, the PLC is programmed in
  relay ladder logic or other easily learned
  languages
• The PLC comes with its program language built
  into permanent memory, whereas a personal
  computer requires a disk operating system (DOS).
  PLC is limited by the language it comes with,
  unless it is a modular type