Chap4 Until End

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Questions and Answers

Which of the following is the most common problem with keyboards?

  • Hardware failure
  • Software malfunction
  • Power supply issues
  • Contact bounce (correct)

What is keybounce?

  • When a key is pressed too softly
  • When a key is pressed too hard
  • When the contacts of a mechanical switch bounce for a short time before staying together (correct)
  • When a key is stuck and won't release

How long does keybounce usually last?

  • 10 to 20 milliseconds (correct)
  • 1 to 2 seconds
  • 1 to 2 milliseconds
  • 10 to 20 seconds

What is the solution to address keybounce?

<p>Wait for the key status to remain stable for 20 milliseconds (C)</p> Signup and view all the answers

What are the two main techniques used to resolve the problem of multiple key presses?

<p>N-key rollover and N-key lock-out (B)</p> Signup and view all the answers

What is n-key rollover?

<p>The hardware mechanism that prevents second and later key closures from generating a strobe until the earlier ones are released (C)</p> Signup and view all the answers

What is n-key lock-out?

<p>The technique of ignoring additional keys which might have been pressed and released (C)</p> Signup and view all the answers

What is the significant cost of n-key rollover protection?

<p>The need for a diode in series with every key (C)</p> Signup and view all the answers

What is the 'phantom key' problem?

<p>The problem of another key seeming to be pressed in addition to the three (B)</p> Signup and view all the answers

What is the simplest and most often used method for n-key lock-out?

<p>The technique of ignoring additional keys which might have been pressed and released (D)</p> Signup and view all the answers

What is the effect of implementing n-key rollover protection without a diode in series with every key?

<p>The keys will work but the accuracy will be lower (B)</p> Signup and view all the answers

What is the solution to the 'phantom key' problem?

<p>Overcome it in software (B)</p> Signup and view all the answers

Which of the following is the most common problem with keyboards?

<p>Contact bounce (B)</p> Signup and view all the answers

What is keybounce?

<p>When the contacts of a mechanical switch bounce for a short time before staying together (A)</p> Signup and view all the answers

How long does keybounce usually last?

<p>10 to 20 milliseconds (D)</p> Signup and view all the answers

What is the solution to address keybounce?

<p>Wait for the key status to remain stable for 20 milliseconds (B)</p> Signup and view all the answers

What are the two main techniques used to resolve the problem of multiple key presses?

<p>N-key rollover and N-key lock-out (B)</p> Signup and view all the answers

What is n-key rollover?

<p>The hardware mechanism that prevents second and later key closures from generating a strobe until the earlier ones are released (D)</p> Signup and view all the answers

What is n-key lock-out?

<p>The technique of ignoring additional keys which might have been pressed and released (C)</p> Signup and view all the answers

What is the significant cost of n-key rollover protection?

<p>The need for a diode in series with every key (A)</p> Signup and view all the answers

What is the 'phantom key' problem?

<p>The problem of another key seeming to be pressed in addition to the three (D)</p> Signup and view all the answers

What is the simplest and most often used method for n-key lock-out?

<p>The technique of ignoring additional keys which might have been pressed and released (A)</p> Signup and view all the answers

What is the effect of implementing n-key rollover protection without a diode in series with every key?

<p>The keys will work but the accuracy will be lower (D)</p> Signup and view all the answers

What is the solution to the 'phantom key' problem?

<p>Overcome it in software (A)</p> Signup and view all the answers

Which type of key press detection technique ignores all key closures until only one key closure is detected?

<p>N-key rollover (D)</p> Signup and view all the answers

What is keybounce?

<p>The resistance of a switch changes when it opens or closes (B)</p> Signup and view all the answers

What is the duration of keybounce?

<p>10 to 20 milliseconds (C)</p> Signup and view all the answers

What is the solution to keybounce?

<p>Wait for the status of a key to remain stable for perhaps 20 milliseconds (A)</p> Signup and view all the answers

What is the purpose of the n-key lockout technique?

<p>To eliminate phantom keys (B)</p> Signup and view all the answers

What is the phantom key problem?

<p>A key that is pressed in addition to the three adjacent keys at a right angle (D)</p> Signup and view all the answers

What is the duration of the delay mechanism used in the second method of n-key rollover?

<p>10 to 20 milliseconds (D)</p> Signup and view all the answers

What is the purpose of the R-C filter used in hardware filtering?

<p>To wait for the status of a key to remain stable for perhaps 20 milliseconds (A)</p> Signup and view all the answers

What is the main difference between the two techniques used to resolve the multiple key press problem?

<p>The n-key rollover technique ignores the reading from the keyboard until only one key closure is detected, while the n-key lockout technique takes into account only one key pressed (B)</p> Signup and view all the answers

What is the effect of pressing three adjacent keys at a right angle?

<p>A phantom key is generated (B)</p> Signup and view all the answers

What is the most common problem in keyboard interfacing?

<p>Contact bounce (B)</p> Signup and view all the answers

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