Re: [SI-LIST] : Spread Spectrum in High Speed Serial Design

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From: jrbarnes@lexmark.com
Date: Mon May 21 2001 - 11:16:19 PDT


XY,
Even though our Dr. Keith Hardin came up with the Spread Spectrum Clock
Generator (SSCG) scheme, we still use fixed-frequency clocks for synchronous
serial data-streams such as:
* 100BASE-TX, 10BASE-T, and 10BASE2 Ethernet.
* Token-Ring.
* Universal Serial Bus (USB).
* LocalTalk.
* Etc.

Asynchronous serial data-streams work okay with an SSCG clock, because the
transmit and receive clocks only have to match within 2-4% to receive a 10- or
11-bit character (start bit, 8 data bits, maybe a parity bit, and stop bit)
depending on the implementation of the receiver.
                                         John Barnes Advisory Engineer
                                         Lexmark International

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