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10 bit Parallel-in Serial-out Shift Register

Discussion in 'Electronics Homework Help' started by Thaahoo, Feb 14, 2015.

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  1. Thaahoo

    Thaahoo

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    Feb 14, 2015
    Hi,
    I want to create a 10 bit parallel in serial out shift register in multisim 12. How can I do it?

    My real aim is to create a Parallel to Serial (RS232) converter. One ASCII visible character loaded in shift register should be be shifted one by one to the the serial output. 10 bits are for the one start bit, 8 data bits and one stop bit.

    Thanks in advance!
     
    Last edited by a moderator: Feb 14, 2015
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Have a look at some datasheets for shift registers. What are they composed of? Once you figure this out, it should be trivial to make one of any length that you require.

    Then look at these individual component parts. How can their state be set other than via the normal action of the shift register? You should then be able to figure out how to do a parallel load,

    (You may also need to consider how you clear the shift register.)
     
    KrisBlueNZ likes this.
  3. Thaahoo

    Thaahoo

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    Feb 14, 2015
    I could set up one using 74HC165 And it is working properly. It is 8 bit. What about a 10 bit one?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Does a 74HC165 have a serial input?
     
  5. Thaahoo

    Thaahoo

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    Feb 14, 2015
    As I know it has Parallel inputs. [​IMG]
     
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Think about Steve's question.
     
  7. Thaahoo

    Thaahoo

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    Feb 14, 2015
    I didn't get you.
     
  8. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    What is the basic logic element that makes up a shift register?

    How are they connected together to provide parallel input, serial input, shifting operation, parallel output, and serial output?

    When you're creating a new device in a simulator or using an FPGA, it's helpful to look at existing devices (e.g. 74xx165, 74xx595) to see how they are implemented, but only so you can understand the internal parts of the device and how they work together to produce the specified behaviour for the device.

    Once you understand that, you can design your shift register using the same arrangement, duplicated the number of times you want.

    If you were designing a circuit to be built from existing devices, then you would need to worry about how to add blocks to the 165 or 595 (or whatever device you based your design around) to extend the number of bits. But in this case, it's simpler to break that device down into its component parts and reassemble a whole new "device" that does exactly what you want.
     
  9. Thaahoo

    Thaahoo

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    Feb 14, 2015
    [​IMG]
    I tried something like this and no shifting happened.
    Please help ShiftRegister.png
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    The bottom end of S1B is connected to earth! I don't know if that's why it isn't working, but it's wrong, so try fixing it!

    Edit: Also, S3 is currently shorting VCC to earth as well.
     
  11. Thaahoo

    Thaahoo

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    Feb 14, 2015
    Tomorrow is the submission date. Can any one help me to make this as a parallel input serial output shift register? The current one is perfectly working as a serial input register.
    [​IMG]
     
  12. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    You already have serial output; all you need is parallel input.

    A simple way to add parallel input is to use the set and reset inputs of the flip-flops. You need to add a single parallel load signal, and a parallel data input for each flip-flop. Your logic needs to take these input signals and generate a set and reset signal for each flip-flop. When the parallel load signal is inactive, the set and reset signals to the flip-flops are held inactive. When the parallel load signal is active, each flip-flop is either set or reset depending on the state of its parallel data input.
     
  13. Thaahoo

    Thaahoo

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    Feb 14, 2015
    Could you please draw the input line? My mind is not working. Exhausted. Thanks in advance.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    The answer is in the 5th post in this thread
     
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