Part 3: Logic IC Replacement

4min
Lead In
In Part 1 and Part 2, we considered the preparatory requirements. In this final part, we will consider the hardware requirements.
The Inputs
From the equation perspective, the code is correct. However, we need to take into consideration how the hardware interacts with the user or the actuator providing the inputs.
One of the issues with the input to PIC is the potential for false triggers. While it would be unlikely for there to be two false triggers at the same time interference on the inputs can cause them not to work or trigger properly.
A common method to negate this would be to pull the inputs high. However, that now means that your inputs are triggered. To implement this, all that would be needed is to negate the logic so that you have !A.!B = 1. 
﻿
C
// Compare the value of the two inputs and if both are high, the equation is true 

if (!PORTB.B0 && !PORTB.B1){
  PORTB.B3 = 1;
}

// Always remember to clear the output or set low

else{
  PORTB.B3 = 0;
}
// Compare the value of the two inputs and if both are high, the equation is true 

if (!PORTB.B0 && !PORTB.B1){
  PORTB.B3 = 1;
}

// Always remember to clear the output or set low

else{
  PORTB.B3 = 0;
}
﻿
In the iteration above, when both inputs are pulled low you then have the same effect. If you noticed that the truth table is out, then you are correct. While there are other ways to implement the above, this is the most cost-effective.
The Output
Driving the output can be a simple LED resistor combination to show that the software is working. The options are there to drive more power-intensive loads.
Lead Out
That brings this section to a conclusion.
Part 2: Logic IC Replacement
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