1 / 9

Digital Systems I

Digital Systems I. EEC 180A Lecture 15 Bevan M. Baas Tuesday, November 20, 2007. Counter Example. 3-bit counter Specification Starting at zero, it increments by 3 at 6, it wraps back to 0 Has a reset signal input When reset =1, the next counter value is 0 Uses D Flip-flops. reset.

alena
Download Presentation

Digital Systems I

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Digital Systems I EEC 180A Lecture 15 Bevan M. Baas Tuesday, November 20, 2007

  2. Counter Example • 3-bit counter • Specification • Starting at zero, it increments by 3 • at 6, it wraps back to 0 • Has a reset signal input • When reset=1, the next counter value is 0 • Uses D Flip-flops reset 0 6 3

  3. Counter ExampleUsing D FFs • State Table • Two different values of reset treated as different Next States in this example reset=0 reset=1 Present State ABC Next State ABC Next State ABC 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset 0 6 3

  4. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC XXX XXX 0 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX output XXX reset 0 “current” time 6 3

  5. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC 000 XXX 1 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX 000 output XXX XXX reset 0 “current” time 6 3

  6. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC 011 000 000 0 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX 000 011 output XXX XXX 000 reset 0 “current” time 6 3

  7. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC 110 011 0 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX 000 011 110 output XXX XXX 000 011 reset 0 “current” time 6 3

  8. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC 000 110 0 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX 000 011 110 000 output XXX XXX 000 011 110 reset 0 “current” time 6 3

  9. Counter ExampleUsing D FFs reset=0 reset=1 Present State ABC Next State ABC Next State ABC 011 000 0 Combina- tionalLogic output (= state) 000 001 010 011 100 101 110 111 011 xxx xxx 110 xxx xxx 000 xxx 000 000 000 000 000 000 000 000 reset DA,B,C clk reset DA,B,C XXX 000 011 110 000 011 output XXX XXX 000 011 110 000 reset 0 “current” time 6 3

More Related