Preliminary
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Introduction
Half Duplex— In half-duplex mode, the CSMA/CD media access method is the means by which two or
more stations share a common transmission medium. To transmit, a station waits (defers) for a
quiet period on the medium, that is, no other station is transmitting. It then sends the intended
message in bit-serial form. If, after initiating a transmission, the message collides with that of
another station, then each transmitting station intentionally transmits for an additional predefined
period to ensure propagation of the collision throughout the system. The station remains silent for a
random amount of time (backoff) before attempting to transmit again.
Host— The host is an intelligent system resource that configures and manages each communications
control module. The host is responsible for allocating memory, initializing all data structures, and
responding to port (EMAC) interrupts. In this document, host refers to the device.
Jabber— A condition wherein a station transmits for a period of time longer than the maximum
permissible packet length, usually due to a fault condition.
Link— The transmission path between any two instances of generic cabling.
Multicast MAC Address— A class of MAC address that sends a packet to potentially more than one
recipient. A group address is specified by setting the LSB of the first MAC address byte to 1. Thus,
01h-02h-03h-04h-05h-06h is a valid multicast address. Typically, an Ethernet MAC looks for only
certain multicast addresses on a network to reduce traffic load. The multicast address list of
acceptable packets is specified by the application.
Physical Layer and Media Notation— To identify different Ethernet technologies, a simple, three-field,
type notation is used. The Physical Layer type used by the Ethernet is specified by these fields:
<data rate in Mb/s><medium type><maximum segment length (×100m)>
The definitions for the technologies mentioned in this document are in
.
Table 3-1. Physical Layer Definitions
Term
Definition
10Base-T
IEEE 802.3 Physical Layer specification for a 10 Mb/s CSMA/CD local area network over two pairs of
twisted-pair telephone wire.
100Base-T
IEEE 802.3 Physical Layer specification for a 100 Mb/s CSMA/CD local area network over two pairs of
Category 5 unshielded twisted-pair (UTP) or shielded twisted-pair (STP) wire.
Twisted pair
A cable element that consists of two insulated conductors twisted together in a regular fashion to form a
balanced transmission line.
Port— Ethernet device.
Promiscuous Mode— EMAC receives frames that do not match its address.
409
SPRUGX9 – 15 April 2011
EMAC/MDIO Module
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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