•  The Idea
•  The Steps Taken
• Inputting the Morse Code
• Translating the Input to Binary
• Storing the Numbers and Performing Addition
• Circuit Diagram
• Board Diagram

The Idea

The idea for our final project for Digital Logic Design was to make a device that accepts two numbers formatted in morse code, add them, and display the output as morse code on seven segment displays.

A brief explanation of morse code is necessary to understand this project.  A component in morse code can be either a short beep, represented by a dot, or a long beep, represented by a dash.  A combination of the dots and dashes is termed a word.  The components must be entered in a specific manner: a dot must consist of one time unit, while a dash must consist of three.  The words in morse code that represent the numbers from zero to nine are:



Thus the number is inputted via a push button switch, which interprets the dots and dashes as ones and zeros respectively.

My partner for this assignment was Martin Raphan, 1 BSE.  His page contains his contribution to our writeup (INTERNAL PAGE ONLY).

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The Steps Taken

We divided this project into a couple of sections as follows:
 
Inputting the Morse Code

 
•  Set up a 4 bit shift register (74194) shifting right with a 555 timer providing the clock.
• The "." and "_" is provided by a push button switch, which gives a low when pressed, and default (High) otherwise.
• Invert the input from the push button switch and put it in the serial right data input of the 74194.
• Take the first 3 parallel outputs from the shift register and AND them together.  The reasoning behind this is to detect when an input consisting of 3 time units is entered.
• Separately, invert the first and third output and AND these together.  This detects a 010 input, signalling that a "." has been entered.
• Display the result on a seven segment display, which lights up the "." when a "." has been entered, and a segment if the "_" has been entered.
 
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LOGIC DIAGRAM



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Translating the Input to Binary
 

• Feed the output from the AND gate that produces a High for a "." into a separate shift register which is clocked when either of the results from the AND gates is a 1.
• Connect a D type flip flop to the shift register to allow for the fifth bit of input, providing it with the same clock as that of the shift register.
• Display the output of the 5 bits on a seven segment display, which lights up a segment when the input is a "_" and turns off a segment when the input is a "."
• Translating the input involves the use of 5 variable karnaugh maps where the function generated is a four bit number from the five inputted bits of morse code.
 
  TRUTH TABLE



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  KARNAUGH MAPS

PLEASE MAXIMIZE YOUR WINDOW FOR PROPER LAYOUT OF THE IMAGES.






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  BOOLEAN EQUATIONS



Since the equation for A was quite complex, the function was generated using an 8-1 line multiplexer (74151).

The address lines for the MUX were M_a, M_b, and M_c (most significant to least significant) and the data inputs were constructed from the following tables:

PLEASE MAXIMIZE YOUR WINDOW FOR PROPER LAYOUT OF THE IMAGES.





The functions generated for the data inputs of the MUX are as follows:


 
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  LOGIC DIAGRAM
 


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Storing the Numbers and Performing Addition
 

• To use a single clock to store the numbers in two separate shift registers, we used a JK flip flop that toggles on the input of the send button and ANDed two distinct combinations which induced rising edges for the 74194.
REFER TO THE CIRCUIT DIAGRAM BELOW FOR THE LOGIC/CIRCUIT OF THIS UNIT

 

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