The discussion revolves around understanding NRZI (Non-Return-to-Zero Inverted) encoding and its relationship with NRZ (Non-Return-to-Zero) and NRZ-I (Non-Return-to-Zero Inverted). Participants explore the definitions, differences, and implications of these encoding schemes, with a focus on their technical aspects and potential confusions.
Participants express differing views on the definitions and implications of NRZI and NRZ-I, indicating that multiple competing interpretations remain. The discussion does not reach a consensus on the terminology or the technical distinctions.
Some participants acknowledge the need for further reading to clarify their understanding of NRZI and NRZ-I, suggesting that there may be unresolved assumptions or definitions influencing the discussion.
That looks close, but the "Inverted" part of NRZI means that you should invert that plot, no?Dan78 said:
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).berkeman said:
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 said:
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).berkeman said:
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!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 |
Looks good to me.Dan78 said:
