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Datasheet 1
Networking Silicon — 82555
1.0 Introduction
The 82555 is a highly integrated, physical layer interface solution designed for 10 and 100 Mbps
Ethernet systems based on the IEEE 10BASE-T and 100BASE-TX specifications. 100BASE-TX is
an IEEE 802.3 physical layer specification for use over two pairs of Category 5 unshielded twisted
pair or Type 1 shielded twisted pair cable. 100BASE-TX defines a signaling scheme not only for
100 Mbps, but also provides CSMA/CD compatibility with the 10 Mbps IEEE 802.3 10BASE-T
signaling standard.
1.1 Functional Overview
The 82555 is designed to work in two modes: Data Terminal Equipment (DTE) for adapters and
repeater for hubs and switches. When configured to DTE (adapter) mode, the 82555 incorporates
all active circuitry required to interface 10/100 Mbps Ethernet controllers and CSMA/CD MAC
components to 10 Mbps and 100 Mbps networks. In this and other documents the 82555 may be
referred to as the DTE, Physical Medium Device (PMD), or Physical Layer Medium (PLM). It
supports a direct glueless interface to Intel components such as the 82557 Fast Ethernet controller.
The 82555 also supports the Media Independent Interface (MII) signals as specified in the IEEE
802.3u standard. The figure below shows how the 82555 fits into a 10/100 Mbps Ethernet adapter
design.
When configured to repeater mode, the 82555 incorporates several features that allow it to function
as a Class I or MII level repeater. Section 6.0, “Repeater Mode” on page 25 describes the 82555 in
a repeater type of application.
1.2 Compliance to Industry Standards
When operating in 100 Mbps mode, the 82555 complies with IEEE 802.3u 100BASE-TX
specification. The PMD section with the related changes established in 802.3u 100BASE-TX
complies with ANSI X3.263:1995 TP-PMD, Revision 2.2.
When operating in the 10 Mbps mode, the 82555 complies with the IEEE 802.3 10BASE-T
specification.
Figure 1. 82555 10/100 Mbps Ethernet Solution
Controller/MAC
Intel 82555
System Bus Interface
Pair 1
Pair 2
Ma
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