Homework for Tuesday, October 5

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Homework for Tuesday, October 5

• Write a solution to the black box problem just
  presented that is based on the 8088 and 8255.

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A Black Box problem
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Solution

• 1) Separate inputs and outputs on the black box
• 2) Determine what kind of signals are used for
  input and output
• Inputs
• Data from the outside worldM1, M0 1s and 0s
  to define the modeSet Mode (positive edge)Start
  (negative edge)
• OutputsMode Begin (positive edge, line goes low
  on Reset mode)Mode End (positive edge, line goes
  low on Reset mode)

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Solution

• 1) Separate inputs and outputs on the black box
• 2) Determine what kind of signals are used for
  input and output
• 3) Allocate resources of the 8255
• Draw the connections

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A Black Box problem
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Flow Chart of Solution
Set 8255 A out, Bin, PCH out, PCL in
Reset DAS
Put DAS in Acquire Data mode
N
Mode BeginHigh?
Y
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Flow Chart, Page 2
Initialize Counter
Delay 200 msec
Increment Counter
N
Mode EndHigh?
Y
N
Y
Al 0FF
Al 00
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