ECET 340 Week 3 HomeWork 3

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DEVRY ECET 340 Week 3 HomeWork 3

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•  1. Sketch a circuit that can be used to debounce
  a pushbutton and explain how it works. (4 points
  max)
• 2. In Figure 7.32 on page 339 of the Huang
  textbook, if the row has and the columnsare ,
  which key is pressed? (2 points max)
• 3. In Figure 7.32 on page 339 of the Huang
  textbook, explain why the 10k? resistors ties to
  VCC are required. (2 points max)

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• 4. Write down the lines of C code (interrupt
  service routine, ISR) that generates an interrupt
  when Port H pin 0 becomes a logic 1. Within
  this ISR, disable interrupts, clear the interrupt
  flag, then enable interrupts, and return from
  routine. I also want the routine or lines of C
  code that initialize Port H pin 0 to be used as
  an interrupt (hint think data direction
  register) (2 points max)
• 5. Write down the C statements you would need to
  add to the main program of the keypad driver
  program given in lecture and lab in order to
  store the key characters to a buffer area of
  memory called keys_entered and exit the program
  as soon as either seven keypresses are entered or
  the the D key is entered. (Counts as two
  questions) (4 points max.you need to use arrays
  in C code)
• 6. State the functions of pins RS, E and R/W in
  the LCD. (4 points max)
• 7. Give the state of RS, E and R/W, and the
  command code (in hex) for the 20th location, line
  2 on the 40x2 LCD described in lecture. (2 points
  max)
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