Ee2 chapter13 counters

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Ee2 chapter13 counters

  1. 1. IT2001PAEngineering Essentials (2/2)Chapter 13 - Counters Lecturer Namelecturer_email@ite.edu.sg Nov 20, 2012Contact Number
  2. 2. Chapter 13 - CountersLesson ObjectivesUpon completion of this topic, you should be able to: Sketch the output waveform of a basic 4 bit up/down counter. IT2001PA Engineering Essentials (2/2) 2
  3. 3. Chapter 13 - CountersSpecific Objectives Students should be able to :  Identify 2 different types of counter :  Ripple up counter and  Ripple down counter  Describe the operation of a 4 bit asynchronous ripple up counter with the aid of a waveform diagram.  Construct the truth table.  State the maximum number of count.  Describe the operation of a basic 4 bit asynchronous ripple down counter with the aid of a waveform diagram. IT2001PA Engineering Essentials (2/2)
  4. 4. Chapter 13 - CountersBinary counting sequence Used to count the • number of binary pulses applied Example: recycles Decimal : 0 1 2 3 0 Binary : 00 01 10 11 00 IT2001PA Engineering Essentials (2/2) 4
  5. 5. Chapter 13 - Counters Calculation of maximum count value of a counter Let N = number of flip-flops M = maximum count reached before a counter recycles. For N number of flip-flops, N • 2 counting states. N Maximum count = 2 - 1 IT2001PA Engineering Essentials (2/2) 5
  6. 6. Chapter 13 - Counters Example:Determine the maximum count for a counter using • 4 flip-flops • 5 flip-flops Solution: Solution: N=4 N=5 Maximum count, Maximum count, M = 2 N- 1 M = 2 N- 1 = 2 4- 1 = = 2 5- 1 = IT2001PA Engineering Essentials (2/2) 6
  7. 7. Chapter 13 - Counters4-Bit Asynchronous Up CounterD J C J B J A J * CLK CLK CLK CLKD K C K B K A K * * All J and K inputs assumed to be 1. IT2001PA Engineering Essentials (2/2) 7
  8. 8. Chapter 13 - CountersTruth Table D C B A Number of clock pulses 0 0 0 0 0 0 0 0 1 1 0 0 1 0 2 0 0 1 1 3 0 1 0 0 4 0 1 0 1 5 0 1 1 0 6 0 1 1 1 7 1 0 0 0 8 1 0 0 1 9 1 0 1 0 10 1 0 1 1 11 1 1 0 0 12 1 1 0 1 13 1 1 1 0 14 1 1 1 1 15 0 0 0 0 16 (recycles) IT2001PA Engineering Essentials (2/2) 8
  9. 9. Chapter 13 - Counters Counter waveformsCLOCK A B C DCounter-waveforms showing frequency division by 2 for each FF. IT2001PA Engineering Essentials (2/2) 9
  10. 10. Chapter 13 - CountersRipple Up Counter All counter is first of all cleared to zeroes by • activating the CLEAR inputs. Then the counter is clocked to count up. B A * All J and K inputs B J A J * assumed to be 1. CLK CLK B K A K * CLK CLK CLK To clear FFs to “0” IT2001PA Engineering Essentials (2/2) 10
  11. 11. Chapter 13 - CountersRipple Down Counter All counter is first of all presetted to ones by • activating the PRESET inputs. Then the counter is clocked to count down. To preset FFs to “1” PS PS PS B A * All J and K inputs B J A J * CLK CLK assumed to be 1. B K A K * IT2001PA Engineering Essentials (2/2) 11
  12. 12. Chapter 13 - CountersRipple Up Counter recyclesBA counts up from 00 --> 01 --> 10 --> 11 --> 00Ripple Down Counter recyclesBA counts down from 11--> 10 --> 01 --> 00-->11 IT2001PA Engineering Essentials (2/2) 12
  13. 13. Chapter 13 - Counters3-Bit Asynchronous Down Counter C J B J A J * CLK CLK CLK C K B K A K * * All J and K inputs assumed to be 1. IT2001PA Engineering Essentials (2/2) 13
  14. 14. Chapter 13 - CountersTruth Table C B A Number of clock pulses 1 1 1 0 1 1 0 1 1 0 1 2 1 0 0 3 0 1 1 4 0 1 0 5 0 0 1 6 0 0 0 7 1 1 1 8 (recycles) 1 1 0 9 1 0 1 10 1 0 0 11 0 1 1 IT2001PA Engineering Essentials (2/2) 14
  15. 15. Chapter 13 - Counters Counter WaveformsCLOCK 1 1 1 1 1 1 1 1 A 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 B 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 C 0 0 0 0 0 0 0 0Counter-waveforms showing frequency division by 2 for each FF. IT2001PA Engineering Essentials (2/2) 15
  16. 16. Chapter 13 - CountersNext Lesson IT2001PA Engineering Essentials (2/2) 16

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