Freescale Semiconductor TWR-MCF52259-Ethenet, Руководство пользователя, Страница: 22 / 166

TM
Freescale Semiconductor Confidential and Proprietary Information. Freescale™ and the Freescale logo are trademarks
of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2006.
21
Ethernet Definition…
Ethernet - http://dictionary.reference.com/search?q=Ethernet
<networking> A local area network first described by
Metcalfe & Boggs of Xerox PARC in 1976. Specified by DEC ,
Intel and XEROX (DIX) as IEEE 802.3 and now recognised
as the industry standard.
Data is broken into packets and each one is transmitted
using the CSMA/CD algorithm until it arrives at the
destination without colliding with any other packet. The
first contention slot after a transmission is reserved for
an acknowledge packet. A node is either transmitting or
receiving at any instant. The bandwidth is about 10 Mbit/s.
Disk-Ethernet-Disk transfer rate with TCP/IP is typically 30
kilobyte per second.
Version 2 specifies that collision detect of the transceiver
must be activated during the inter-packet gap and that when
transmission finishes, the differential transmit lines are
driven to 0V (half step). It also specifies some network
management functions such as reporting collisions , retries
and deferrals .
Ethernet cables are classified as "XbaseY", e.g. 10base5,
where X is the data rate in Mbps , "base" means " baseband "
(as opposed to radio frequency ) and Y is the category of
cabling. The original cable was 10base5 ("full spec"),
others are 10base2 ("thinnet") and 10baseT ("twisted
pair") which is now (1998) very common. 100baseT (" Fast
Ethernet ") is also increasingly common