As a part of my coursework I need to understand explain and draw a bi-directional shift register. However after a lot of googling I'm finding it difficult to understand it works and the diagrams for it are different done with a single input and sobne with double.

Thank you

 

hi,
Study this HEF40194 PDF.

E

 

hi,
Study this HEF40194 PDF.

E

Thank you for that , but I've read this before and I find it quite confusing , is there any other simpler explanation ? Or if someone can explain it to me please

 

OK then read this first. After understanding it then it would be easier to understand how the 40194 works...

http://www.allaboutcircuits.com/vol_4/chpt_12/4.html

Allen

 

Can you describe, in words, what a bi-directional shift register is or does?

Take you best shot at it and let's work from there.

 

Can you describe, in words, what a bi-directional shift register is or does?

Take you best shot at it and let's work from there.

Okay so I know it can data in, and output data , from what I saw it's only serial in. It uses a control left/right line with gates that can shift data right and left depending on the logic value of the control line. It is rising edge triggered with clock pulse and uses d type flip flops. That's everything I think is right

 

Okay so I know it can data in, and output data , from what I saw it's only serial in. It uses a control left/right line with gates that can shift data right and left depending on the logic value of the control line. It is rising edge triggered with clock pulse and uses d type flip flops. That's everything I think is right

That's a good start. Now see if you can refine that a bit. Think (and describe) it in terms of a chain of registers. If the control bit is telling it to shift left, then on the rising clock edge the contents of all of the registers in the chain are transferred to the register to their left while the input data is put in the right-most register and the output is equal to what is in the leftmost register. If the control bit is telling it to shift right, the same things happen but in the other direction.

So see if you can build up the pieces of it. First, make a chain of three registers that shift from left-to-right on each clock edge. Then see if you can make a chain of three registers that either shift right or shift left depending on the value of a control signal. Then see if you take the output from the leftmost register or the rightmost register depending on the value of a control signal. Then see if you can route an input signal to either the leftmost register or the rightmost register depending on the value of a control signal.

 

That's a good start. Now see if you can refine that a bit. Think (and describe) it in terms of a chain of registers. If the control bit is telling it to shift left, then on the rising clock edge the contents of all of the registers in the chain are transferred to the register to their left while the input data is put in the right-most register and the output is equal to what is in the leftmost register. If the control bit is telling it to shift right, the same things happen but in the other direction.

So see if you can build up the pieces of it. First, make a chain of three registers that shift from left-to-right on each clock edge. Then see if you can make a chain of three registers that either shift right or shift left depending on the value of a control signal. Then see if you take the output from the leftmost register or the rightmost register depending on the value of a control signal. Then see if you can route an input signal to either the leftmost register or the rightmost register depending on the value of a control signal.

Right thank you for this I'll try this. how would I try this on yenka, as in how would I put serial data in on it ?

Thank you again for this

 

I have no idea what "yenka" is, so can't help you there.

 

I am abit confused on how if the data is being shifted left, what happens to the data output? As the output is in the is in the right most flip flop?

 

Hello WBahn,

Yenka is a series of simulation programs:
http://yenka.com/en/Products/

Bertus

 

I am abit confused on how if the data is being shifted left, what happens to the data output? As the output is in the is in the right most flip flop?

When the data is being shifted LEFT, the output data is NOT in the rightmost flip flop.

 

sorry I've got bit confused now! Can you please tell me explain how he output works when being shifted both ways?

 

sorry I've got bit confused now! Can you please tell me explain how he output works when being shifted both ways?

Take a step back and let's say that I have a black box that has two outputs, 'left' and 'right'. I also have a control input called 'dir'. Can you use that black box as part of a larger circuit that has a single output, 'out', that is equal to 'left' if 'dir' is LO and equal to 'right' if 'dir' is HI?

 

Take a step back and let's say that I have a black box that has two outputs, 'left' and 'right'. I also have a control input called 'dir'. Can you use that black box as part of a larger circuit that has a single output, 'out', that is equal to 'left' if 'dir' is LO and equal to 'right' if 'dir' is HI?

yes you can

 

yes you can

Okay, so what does that tell you about how you can get the output value of your bidirectional shift register?

 

 

we can use it as part of a bigger shift register with one output? Im sorry i get confused easily when understanding stuff: i think i understand what you're trying to say, however i am confused about: (e.g. serial in serial out 4 bit bi-diretcional shift register) if i was to pass the data 1010 through it shifting both ways I'm not sure how it'll work as the data line is connected to first and last flip flop and theres one output. i have attached a picture of the diagram i am talking about if this helps. Thank you

 

Read the eText on shift registers:

http://www.allaboutcircuits.com/vol_4/chpt_12/1.html

You cannot shift both ways at the same time. Choose one way, right or left.

 

As with many things, it comes down to what you want -- specifically, what the desired behavior of the system is. You can have different specifications for things that are reasonably given the same name. The specs are what count, not the name.