72APPENDIX A: SPECIFICATIONS AND CABLING REQUIREMENTS

100BASE-TX Operation

100BASE-TX is the IEEE 802.3u standard for Fast Ethernet signaling over Category 5 UTP or STP wire at 100 Mbps.

Based on an extension to the IEEE 802.3 Ethernet specification, Fast Ethernet characteristics include:

A data rate of 100 Mbps.

A broadcast architecture.

A specific media-access control (MAC) scheme.

A wiring topology using 100BASE-TX specifies a wiring hub, cable arranged in a star configuration, and Category 5 UTP or STP wiring. Each node has a separate cable run that must not exceed 100 meters (328 ft) from the node to the hub.

RJ-45 Connector Pin Assignments

Figure 14 shows the RJ-45 connector pin assignments for the 3C905C NIC.

Figure 14 RJ-45 Connector Pin Assignments

TX

 

DATA

ACT

 

10

L

100

N

K

 

1TD+

2TD_

3RD+

6RD_

1 2 3 4 5 6 7 8

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3Com 3C905C-TX-M, 3C905C-TX manual RJ-45 Connector Pin Assignments, 100BASE-TX Operation