logisim homework help

Discussion in 'Homework Help' started by Uyet123, Feb 26, 2015.

  1. Uyet123

    Thread Starter New Member

    Jan 25, 2015
    29
    0
    Question 1: Create a Gray Counter that will accept an input value from the user and commence counting from that location displaying the output to an easy to read and see display. As part of this sequence, the count should restart at 0 and continue until either disabled or the clock is stopped
    Gray Code Sequence: 0 - 1 - 3 - 2 - 6 - 7 - 5 - 4 - 12 - 13 - 15 -14 - 10 - 11 - 9 - 8 - 0

    Create the State Diagram for the above sequence
    Create the State Table for the above sequence
    Create the above in LogiSim using appropriate Flip Flops as subcircuits.

    Question 2: Modify the above circuit so that it stores the state as gray code but displays the count on a hex digit display as the corresponding binary number
    Create the Gray to Binary convertor as a sub-circuit
    Correctly add a Gray to Binary convertor to the circuit

    I am currently stuck in part B because I do not know how to connect it to a hex digit display, its giving me an error saying incompatible width. Here is what I have so far. Question 1 is from the left until the d flip flops output, and question 2 the gray to binary converter is the rest.

    circ.png
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,747
    4,796
    How many inputs does a HEX display require?

    What is another common name for a HEX display?
     
  3. Uyet123

    Thread Starter New Member

    Jan 25, 2015
    29
    0
    It takes 2 inputs, the left bottom wants a 4 data bit input and the right bottom 1 data bit input and only lights up the decimal point.

    I do not know any other name for it.
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,747
    4,796
    It is called a "7-segment display".

    If it takes a 4-bit input for the segments, then it apparently has the decoder built in. Not surprising in a sim model, I guess.

    So how are you trying to connect things up?
     
  5. Uyet123

    Thread Starter New Member

    Jan 25, 2015
    29
    0
    Ah yes, I know what a 7 segment display is. But isn't it different from a hex display, a 7 segment only displays 0-9 while the hex displays more?

    Well, the connections is where I am stuck, according to question 2 the count should be displayed on a hex display. The count is the output from the gray to binary converter, which gives me an error when I connect it with a hex display. So, basically what I want is for the output to be displayed on the hex display instead of 4 LEDS/binary number.
     
  6. WBahn

    Moderator

    Mar 31, 2012
    17,747
    4,796
    A 7-segment display is a display with seven segments arranged in the classic "number eight" configuration. It can display 128 unique patterns (including blank). You generally use a decoder to map between each input pattern and the pattern you want displayed for that input. If you use a 7447 or 7448 BCD decoder, then you take a 4-bit input and map that to 16 of the 128 patterns. The first ten of those look like the decimal digits and the remaining six are pretty much garbage. If you use a hex decoder, then the sixteen 4-bit input patterns map to display patterns that look like the sixteen hexadecimal digits. The point being that it is the decoder that determines what gets displayed, not the display itself. In this case, the assumption is that in this simulator, this part is a combination of a 7-segment display and a hex decoder.

    I'll ask again: How are you trying to connect it to the hex display? How can we possibly tell you what the error you are making is when you won't show us what you are doing? All you have given us is a schematic that has the HEX display sitting off to the side completely unconnected! We are NOT mind readers?
     
  7. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    A seven-segment display will display whatever you drive it with. It is the decoder that drives the display with the appropriate signals, given a set of inputs.

    Here is an example I made in LogiSim for a MOD-10 counter:
    [​IMG]

    The lookup table/ROM serves the purpose of the decoder. To make the seven segment display show A-F, the ROM would have to have to drive the signals appropriately.

    It looks like your display is expecting a bus...
     
    absf likes this.
Loading...