Plesiochronous

The term Plesiochronous is derived from the Greek "plesio", meaning near, and "chronos", time, and refers to the fact that plesiochronous systems run in a state where different parts of the system are almost, but not quite perfectly, synchronised.

According to ITU-T standards, corresponding signals are plesiochronous if their significant instants occur at nominally the same rate, with any variation in rate being constrained within specified limits. In general, plesiochronous systems behave similarly to synchronous systems, except that they must have some means to cope with "sync slips", which will happen at intervals due to the plesiochronous nature of the system.

The most common example of a plesiochronous system design is the Plesiochronous Digital Hierarchy networking standard. The well known Asynchronous serial communication is asynchronous only on byte level, but plesiochronous on the bit level.

The modern tendency in systems engineering is towards using systems that are either fundamentally asynchronous (such as Ethernet), or fundamentally synchronous (such as SDH), and layering these where necessary, rather than using a mixture between the two in a single technology.

A sender and receiver operate plesiosynchronous if they operate at the same nominal frequency but may have a slight frequency mismatch, which leads to a drifting phase [P. Teehan, M. Greenstreet, G. Lemieux: A Survey and Taxonomy of GALS Design Styles, IEEE Design & Test of Computers September-October 2007, p.419] [S. Johnson, S. Scott: A Supercomputer System Interconnect and Scaleble IOS, 14th IEEE Symposium on Mass Storage Systems, 1995, Footnote on p.358]

ee also

* Clock drift
* Jitter
* Wander
* Buffer (telecommunication)

References

"Contains material from FOLDOC, used with permission"


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • plesiochronous — adjective (communications) of or pertaining to the use of clocks derived from similar, but not the same reference clocks The DS 3 standard uses bit stuffing to allow the clocks of its tributaries to be plesiochronous …   Wiktionary

  • plesiochronous — (fast synchron) Datenübertragung mittels analoger Verstärker (nicht verzögerungsfrei) …   Acronyms

  • plesiochronous — (fast synchron) Datenübertragung mittels analoger Verstärker (nicht verzögerungsfrei) …   Acronyms von A bis Z

  • Plesiochronous difference — In telecommunications, if two digital signals are plesiochronous, their transitions occur at nearly the same rate, with any variation being within preset limits. EXAMPLE: If two networks are working together their clocks may be using two… …   Wikipedia

  • Plesiochronous Digital Hierarchy — The Plesiochronous Digital Hierarchy (PDH) is a technology used in telecommunications networks to transport large quantities of data over digital transport equipment such as fibre optic and microwave radio systems. The term plesiochronous is… …   Wikipedia

  • Plesiochronous data hierarchy — Hiérarchie numérique plésiochrone Pile de protocoles 7 • Application 6 • Présentation 5 • Session 4 • …   Wikipédia en Français

  • Plesiochronous digital hierarchy — Hiérarchie numérique plésiochrone Pile de protocoles 7 • Application 6 • Présentation 5 • Session 4 • …   Wikipédia en Français

  • PDH — Plesiochronous Digital Hierarchy (Computing » Telecom) Plesiochronous Digital Hierarchy (Computing » Networking) **** Professional Development Hours (Business » Positions) ** Professional Development Hour (Business » Positions) * Procuraduría de… …   Abbreviations dictionary

  • PDH — • Plesiochronous Digital Hierarchy • Planned Derated Hours ( > IEEE Standard Dictionary ) • Pocket Dosimeter, High NASA …   Acronyms

  • Building Integrated Timing Supply — (BITS), also called Building Integrated Timing System, is a method for distributing a precision clock among telecommunications equipment. The physical medium is a T1/E1 (DS1) line. Faster networks depend on accurate timing. As the number of bits… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.