Is the Scrambler Function in JESD204B Part of the Data Link Layer?

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Discussion Overview

The discussion centers on the classification of the scrambler function within the JESD204B standard, specifically whether it is part of the data link layer or the physical layer. Participants explore the implications of this classification in terms of data transmission and compliance with the OSI model.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that the scrambler function in JESD204B is part of the data link layer, arguing that scrambling occurs before frame alignment and thus relates to bits, bytes, and frames.
  • Others argue that the scrambler is part of the physical layer, stating that the data link layer is concerned with higher-level constructs and does not include scrambling functions.
  • A participant mentions that the scrambler is intended to prevent DC components in the data stream, which could complicate clock extraction during transmission.
  • Another participant references the 8b-10b coding in JESD204B for DC balance and suggests that the optional scrambling is for electromagnetic compliance.
  • One participant cites a source from Analog Devices to support the claim that the scrambler is in the link layer, while another references the OSI model to argue against this classification.

Areas of Agreement / Disagreement

Participants express conflicting views on whether the scrambler function is part of the data link layer or the physical layer, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants reference the OSI layer model and specific functionalities of the data link layer, highlighting potential discrepancies in how JESD204B aligns with these definitions. There are also mentions of specific technical functions, such as DC balance and electromagnetic compliance, which may influence the classification of the scrambler.

senmeis
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Hi,

in some standards such as JESD204B or DVB-S2 a so called scrambler function is defined. As far as I understand this scrambler is a means of spreading spectrum but in data link layer. Is it correct?

Senmeis
 
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I think it will prevent a series of zeros creating a DC component, which the transmission system cannot handle and which wil make clock extraction a problem. The data stream might be disconnected during maintenance, say.
 
Actually tech99 OP is correct. JESD204B has 8b-10b coding in the standard for DC balance. The optional scrambling is for EM compliance.
 
senmeis said:
As far as I understand this scrambler is a means of spreading spectrum but in data link layer.
No. It is in the physical layer. The data link layer deals with bits, bytes and frames.
 
Svein said:
No. It is in the physical layer. The data link layer deals with bits, bytes and frames.

This may be down into the weeds (and not sure if anyone is following this thread) but OP is actually correct. In JESD204B the scrambler is in the link layer as scrambling happens before frame alignment (so we are dealing with bits, bytes, and frames here). See this discussion by Analog Devices:

https://www.analog.com/en/technical-articles/understanding-layers-in-jesd204b-specification.html
 
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analogdesign said:
In JESD204B the scrambler is in the link layer as scrambling happens before frame alignment
Then JESD204B does not conform to the OSI layer model. From Wikipedia (https://en.wikipedia.org/wiki/Data_link_layer):

The services that the data link layer provides are:
 

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