isochronous
<communications> /i:-sok'rn-*s/ A form of multiplexing that guarantees to
provide a certain minimum data rate, as required for time-dependent data such as
video or audio.
Isochronous transmission transmits asynchronous data over a synchronous data
link so that individual characters are only separated by a whole number of
bit-length intervals. This is in contrast to asynchronous transmission, in which
the characters may be separated by arbitrary intervals, and with synchronous
transmission [which does what?].
An isochronous message protocol assigns each data source a fixed amount of time
to transmit (its "slot") within each cycle through the sources. That guarantees
that each source will have regular opportunities to transmit the latest
information. If a source has no more data to transmit, then the rest of its time
slot is wasted. If it has more to send than will fit in its slot, it has to
either store the excess data and transmit it in its next slot, or discard it.
Note that whether messages are isochronous or asynchronous is independent of
whether the transmision of individual bits is synchronous or asynchronous.
Isochronous communication suits applications where a steady data stream is more
important than completeness and accuracy, e.g. video conferencing.
Asynchronous Transfer Mode and High Performance Serial Bus can provide
isochronous service.
Compare: plesiochronous.
[ANIXTER, LAN Magazine 7.93]
(2006-06-13)
Nearby terms:
ISO 9735 « ISOC « ISO C « isochronous »
isochronous transfer » ISODE » ISO Development
Environment
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