Comp Sci Tips for Making Exercise Easy and Enjoyable

[Dan78]

Homework Statement

Using the grid below, sketch a waveform to show how the data 10101000 would be transmitted to line using Non-return-to-zero inverted (NRZI) line encoding. Assume the signal level is initially high as shown.

Relevant Equations

None

 

[berkeman]

You need to show your attempt at this problem. I thought that I made that clear in my previous PM to you...

 

[berkeman]

If you are having trouble understanding NRZI encoding, a Google search can be helpful to get you started:

https://www.google.com/search?q=nrzi+encoding&ie=utf-8&oe=utf-8&client=firefox-b-1

 

[Dan78]

Sorry. What i have is this

 

[berkeman]

Sorry. What i have is this

That looks close, but the "Inverted" part of NRZI means that you should invert that plot, no?

From the Google search preview:

 

[pbuk]

That looks close, but the "Inverted" part of NRZI means that you should invert that plot, no?

I think the "I" is more complicated than that - it doesn't just invert the levels of NRZ, it is a completely different (and poorly named) edge-based system (an edge of either sign is a 1 and the absence of a signal edge on a clock pulse signifies a 0).

https://en.wikipedia.org/wiki/Non-return-to-zero#Non-return-to-zero_inverted
Edit: I don't normally like videos but this one is really clear:

 

[berkeman]

I think the "I" is more complicated than that - it doesn't just invert the levels of NRZ, it is a completely different (and poorly named) edge-based system

Interesting. I only briefly looked at the Wikipedia article for NRZI, which looked like simple inversion. I wonder if NRZ-I is different from NRZI... Guess I need to do some more reading...

 

[pbuk]

Interesting. I only briefly looked at the Wikipedia article for NRZI, which looked like simple inversion. I wonder if NRZ-I is different from NRZI... Guess I need to do some more reading...

As I understand it NRZ-I and NRZ(I) are the same thing as NRZI: I have only ever seen it called NRZI (e.g. in the USB 2.0 specification) and importantly the "I" originally stood for IBM and was nothing to do with inversion (see http://ibm-1401.info/223-6988-729-MagTapeCE-InstRef-62-r.pdf).

This is totally different from NRZ, also called "on-off keying" where 1 is normally represented by a high voltage and 0 a low voltage: I am not aware of the opposite convention having a specific name, I suppose you could call it "Inverted NRZ" but that would just add to the confusion!

In summary

Data 0​	Data 1​	​	​
L​	H​	NRZ​	​
H​	L​	NRZ​	​
No transition​	Transition (H-L or L-H)​	NRZI​	NRZ IBM​
Transition (H-L or L-H)​	No transition​	NRZI​	USB, USB 2​

 

[Dan78]

What about now.
I have a starting point which is higher voltage level and every time when I encounter a 1 i have to change a voltage level. Hope is good now.

 

[pbuk]

every time when I encounter a 1 i have to change a voltage level.

Looks good to me.