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Signals, Circuits, and Computers John Athanasiou Part A Spring 2010

Signals, Circuits, and Computers John Athanasiou Part A Spring 2010. Based on Ping Hsu’s Original Notes. Electricity . Used to deliver energy: Lights Heat (electric oven, microwave oven, electric heater, hair dryer, etc.) Motion (fan, elevator, washing machine…)

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Signals, Circuits, and Computers John Athanasiou Part A Spring 2010

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  1. Signals, Circuits, and ComputersJohn AthanasiouPart ASpring 2010 Based on Ping Hsu’s Original Notes (c) P. Hsu 2007

  2. Electricity Used to deliver energy: • Lights • Heat (electric oven, microwave oven, electric heater, hair dryer, etc.) • Motion (fan, elevator, washing machine…) Used for representation and processing of information • Computer, TV, radio, cell phone… (c) P. Hsu 2007

  3. What is a ‘signal’? A signal is a voltage (or current) that represents a quantity or a piece of information. Examples: • The voltage across the door bell or light bulb • The voltage across the speedometer (car speed) • The voltage across the earphone lines • The voltage across the printer cable wires (a message) (c) P. Hsu 2007

  4. Types of Signals • Analog: A dimmer light switch continuously increases/decreases the current. • Digital : An On/Off light switch applies a fixed, predetermined voltage. (c) P. Hsu 2007

  5. Analog Signal & Digital Signal An analog signal’s voltage (or current) level represents a physical quantity. 4 5 3 2 1 The current represents the water level. 1. Higher water level => 2. higher float position => 3. lower resistance => 4. higher current (V/R) => 5. higher current meter reading => higher water level reading (c) P. Hsu 2007

  6. Digital Signal A digital signal carries information by the state (high or low) of the voltage level. (c) P. Hsu 2007

  7. Voltage Level vs. Logic State Digital Signal has a high noise immunity level – the level of noise that can be added to the signal without affecting its state. (c) P. Hsu 2007

  8. The Apple’s Logo What message does it display? (c) P. Hsu 2007

  9. Bits, Bytes and Words Bits: (20) One ‘bit’ can only represent a binary state: 0 or 1, on or off, stop or go. Bytes. (23) One byte consists of 8 bits. Words: (24 or 25) One word consists of 16 bits (or 32 bits, depending on the computer). (c) P. Hsu 2007

  10. A 4-bit binary number LSB MSB Binary number: 0110 = 0+4+2+0=6 Binary number: 1101 = 8+4+0+1=13 • MSB = Most Significant Bit, • LSB = Least Significant Bit (c) P. Hsu 2007

  11. 4-bit Binary Number ON OFF ON ON Binary Number = 1 0 1 1 Value = 8*(1)+ 4*(0)+2*(1)+1*(1) = 8+2+1 =13 (c) P. Hsu 2007

  12. Binary Code • In a computer, a binary number is used to represent: • Numerical values • Characters and symbols (A, a, ¥,+, ﮗ, @, ….) • Picture, sound, video, etc. • Machine language (for math operations, etc.) • others … (c) P. Hsu 2007

  13. An example of a binary coding (c) P. Hsu 2007

  14. Q1: What is the decimal value of the 4-bit binary number 0101? • 3 • 4 • 5 • 6 • 7 (c) P. Hsu 2007

  15. Q2. What do we call the bit that is in the leftmost position in a binary number? A: SNB B: LMB C: MSB D: LSB E: USB (c) P. Hsu 2007

  16. (c) P. Hsu 2007

  17. Parallel connection: a dedicated wire for each bit (needs a lot of wires). Digital Communication (c) P. Hsu 2007

  18. Serial connection: bits are sent sequentially (takes long time ). Digital Communication (c) P. Hsu 2007

  19. Sending a byte or a word in parallel, sequentially (commonly used between circuits within a computer) (c) P. Hsu 2007

  20. Analog Signal vs. Digital Signal 1. Analog signals Pros: high resolution, efficient transmission (1 wire, 1 signal), no delay, ‘real world’ signals. Cons: Difficult to process (perform operations, storage), susceptible to noise. 2. Digital Signals Pros: high immunity to noise, easy to process Cons: needs a lot of ‘bits’ and circuits, data processing delay (c) P. Hsu 2007

  21. Analog – Digital Conversion Bit 0 Digital input DAC Analog output Bit 9 Bit 0 Digital output ADC Analog input Bit 9 (c) P. Hsu 2007

  22. Q3. Which of the following is NOT an advantage of a digital signal: A: Easy to perform math operation B: Easy to store C: High noise immunity D: Need less circuitry. E: All the above (c) P. Hsu 2007

  23. VEX Microcontroller CPU: Executing instructions, performing arithmetic and logic operations. It is the ‘brain’ of the computer. Memory: Memory is for keeping program and data. IO Port: Gateway to and from the external devices. (c) P. Hsu 2007

  24. VEX controller IO Ports Analog/Digital Port (16 ports) Interrupt Ports Motor Ports (8 ports) (c) P. Hsu 2007

  25. Infrared Emitting Beacons • The beacons used in this project ‘flash’ infrared light at 1kHz(the red one) and 10kHz(the green one). • This flashing light allows the receiver circuit to • tune to the targeted beacon and • distinguish the light emitted by the beacons from the ambient light. (c) P. Hsu 2007

  26. Infrared Receiver Board Tune to 1kHz or 10kHz For each active exposure control, counter increases by 1. For selecting one of the 8 infrared detectors (c) P. Hsu 2007

  27. Q4: What is the abbreviated name of the circuit in a computer that performs arithmetic operation? A: USB B: AOU C: CPU D: AIO E: MOU End of Part A. (c) P. Hsu 2007

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