# Universal Shift Register

#### iwanna4get

Joined Feb 13, 2013
2
Ok we have Three Homework to make.

To make applications of
1.) Ripple Counter
2.) Johnson Counter
3.) Universal Shift Register

So in order to make application of said experiments I have to study them so I did.

I understood Ripple Counter and Johnson Counter, but I don't understand Universal Shift Registers.

This is the circuit. I understand the table and what I don't understand is ;

1.) What is the serial input for shift-right and serial input for shift- left is for?
2.) How does it affect the circuit?
3.) How come only there only seems to be 1 set of 4-bit input in the mux(where is the other selection of 4-bit input)?
4.) When it shifts to the left or right does it continously shift until all output is zero (example: input is 0101 ; Sequence : 0011 , 0110, 1100 , 1000, 0000) or does it loop (example: input is 0101 ; Sequence : 0011 , 0110, 1100 , 1001, ... and so on)
5.) How does it shift serial input?

#### tshuck

Joined Oct 18, 2012
3,535 I understand the table and what I don't understand is ;

1.) What is the serial input for shift-right and serial input for shift- left is for?
2.) How does it affect the circuit?
3.) How come only there only seems to be 1 set of 4-bit input in the mux(where is the other selection of 4-bit input)?
4.) When it shifts to the left or right does it continously shift until all output is zero (example: input is 0101 ; Sequence : 0011 , 0110, 1100 , 1000, 0000) or does it loop (example: input is 0101 ; Sequence : 0011 , 0110, 1100 , 1001, ... and so on)
5.) How does it shift serial input?
1.)The serial input is so that you can shift data into the shift register. This is what makes it a universal shift register; it can shift in either direction, do parallel input & parallel output
2.)It allows serial data to be put into the registers
3.) I don't know what you are trying to say here.

If you are asking why there is one set of 4-bit inputs, why would there be more? these inputs are a parallel load, allowing the shift register to be loaded with a 4-bit value which would, most likely, be shifted out of the register.
4. & 5.) You tell me. Is this not Homework Help? Go through the same sequence you suggested. make s1 = 1 and s0 = 0. put your values in and fill out a table representing the outputs. You must learn to trace the logic and determine the states of the device.

As a side note, you are asking about whether the shift register does a shift(does not wrap data back into itself) and rotating(wraps data back into itself).

#### iwanna4get

Joined Feb 13, 2013
2
1.)The serial input is so that you can shift data into the shift register. This is what makes it a universal shift register; it can shift in either direction, do parallel input & parallel output
2.)It allows serial data to be put into the registers
3.) I don't know what you are trying to say here.

If you are asking why there is one set of 4-bit inputs, why would there be more? these inputs are a parallel load, allowing the shift register to be loaded with a 4-bit value which would, most likely, be shifted out of the register.
4. & 5.) You tell me. Is this not Homework Help? Go through the same sequence you suggested. make s1 = 1 and s0 = 0. put your values in and fill out a table representing the outputs. You must learn to trace the logic and determine the states of the device.

As a side note, you are asking about whether the shift register does a shift(does not wrap data back into itself) and rotating(wraps data back into itself).

What I meant is the 4x1 mux itself. with the number 0 1 2 3.

But I am a complete idiot -.- .

I mixed up the input and output ~ Gah

Thanks about for answering number 2 I thought it was connected to S1 and S0 #### tshuck

Joined Oct 18, 2012
3,535
But I am a complete idiot -.- .
No. You are not a complete idiot. Even if you don't believe that, it's important to understand that you can grasp concepts others would faint simply thinking about Have a little more confidence!

Actually, I've never seen it done this way, so it took me a minute to understand its operation....