Networking Connectivity
Network Connectivity
100 Mbps cabling specifications

Intel® PRO adapters have a small, snap-in RJ45 connector. RJ45 cabling is also known as Twisted-pair Ethernet (TPE), Unshielded twisted pair (UTP), and 10BASE-T cabling. The type of cabling you must use depends on the adapter you're using.

This document covers the following topics:

  • Important Cabling Basics
  • 100BASE-TX adapters
  • 100BASE-T4 adapters (EtherExpress™ PRO/100B T4 only)
  • Connecting 2 stations without a hub
  • Link integrity
  • Common problems
Note For 10 MBPS operation, refer to the 10 MBPS cabling specifications help file.

Important Cabling Basics
The cable must comply with the IEEE 802.3 10BASE-T standard for 2-pair, UTP cable. For 100BASE-TX the cable must be category 5. For 100BASE-T4 the cable must be category 3 or higher.

The cable between the computer and the hub must be less than 100 meters long.

Each signal requires a wire pair (+ and - signal polarities). The term "pair" refers to 2 wires, typically of a common color base, twisted around each other within the larger cable. If you split the + and - signals so that each on is part of a different pair, then the cable may seem to work at 10 megabits per second (10BASE-T) but not at 100 except for short lengths (under 5 meters).

You should maintain the polarity of the wires from end to end (i.e. the wire connected to pin 1 at one end should connect to pin 1 at the other end, etc.).

Intervening cabling hardware, such as punch down blocks and wall plates, must match or exceed the category rating of the cable.

When untwisting the wire pair in preparation for crimping, you should not untwist the wire more than 1/2 inch (~1½ turns).

100BASE-TX Adapters

Cable and Connector Pinouts
If you need to repair a cable or provide connectors for UTP cable, wire straight through as shown in the following table.

Function Pin# Pin#
TX+ 1 1
TX- 2 2
RX+ 3 3
RX- 6 6

(This is an MDI, or straight through, cable.)

Pins 1 and 2 must be a pair, and pins 3 and 6 must be a pair. The term "pair" refers to 2 wires, typically of a common color base, twisted around each other within the larger cable.

To allow for a straight-through cable, the hub provides an internal transmit/receive crossover function. This means the transmit circuit of the network card is connected to the receive circuit of the hub and vice versa.

Pinout for the RJ45 connector (suggested wire colors)

1 |-- | 8 |brown or brown/white---|\
2 |-- | 7 |--white/brown--------------| \
3 |-- ---- 6 |green or green/white----|  \
4 |--     | 5 |blue or blue white--------|   -
5 |--     | 4 |--white/blue-----------------|   _CABLE
6 |-- ---- 3 |--white/green---------------|  /
7 |-- | 2 |orange or orange/white-| /
8 |-- | 1 |--white/orange--------------|/
VIEWED FROM END VIEWED FROM TOP (opposite the retaining clip)

Pin Name and Function:

  1. Transmit Data Plus (TD+): The positive signal for the TD differential pair. This signal contains the serial output data stream transmitted onto the network.

  2. Transmit Data Minus (TD-): The negative signal for the TD differential pair. This contains the same output as pin 1.

  3. Receive Data Plus (RD+): The positive signal for the RD differential pair. This signal contains the serial input data stream received from the network.

  4. Not used.

  5. Not used.

  6. Receive Data Minus (RD-): The negative signal for the RD differential pair. This signal contains the same input as pin 3.

  7. Not used.

  8. Not used.

100BASE-T4 Adapters (EtherExpress™ PRO/100B T4, model PILA8475B only)
When operating at 100 MBPS, the cable must comply with the IEEE 802.3u 100BASE-T4 specification. The cable between the computer and the hub must be less than 100 meters long.

Cable and Connector Pinouts
Unlike TX cabling, T4 cabling does not use separate, dedicated pairs to transmit or receive data. T4 cabling uses all four pairs of wires. Three pairs are used to transmit data, while the fourth pair is used to detect collisions.

Pin pairings are as follows:

Pin# Signal
1 TX_D1+
2 TX_D1-
3 RX_D2+
4 BI_D3+
5 BI_D3-
6 RX_D2-
7 BI_D4+
8 BI_D4-

Pins 1 and 2 must be a pair.
Pins 3 and 6 must be a pair.
Pins 4 and 5 must be a pair.
Pins 7 and 8 must be a pair.

To allow for a straight-through cable, the hub provides an internal transmit/receive crossover function. This means the transmit circuit of the network card is connected to the receive circuit of the hub and vice versa.

Connecting Two Workstations Without a Hub
100BASE-T uses a star topology. This means a hub or concentrator is in the center of a star, and each workstation or server is connected to this hub.

For test purposes, you can directly connect two workstations or a workstation and a server without using a hub. This setup requires a special cable incorporating the crossover function described earlier in this document. The tables below show which wires need to be crossed over.

100BASE-TX crossover cable diagram

Function Pin# Pin# Function
TX+ 1 3 RX+
TX- 2 6 RX-
RX+ 3 1 TX+
RX- 6 2 TX-

(This is an MDI-X, or crossover, cable.)

The receive data pair (the two wires designated RD) must be a twisted pair, and the transmit data pair (designated TD) must be a twisted pair.

100BASE-T4 crossover cable diagram

Pin# Signal Signal Pin#
1 TX_D1+ RX_D2+ 3
2 TX_D1- RX_D2- 6
3 RX_D2+ TX_D1+ 1
4 BI_D3+ BI_D4+ 7
5 BI_D3- BI_D4- 8
6 RX_D2- TX_D1- 2
7 BI_D4+ BI_D3+ 4
8 BI_D4- BI_D3- 5

The receive data pair (the two wires designated RX_D2) must be a twisted pair. The transmit data pair (designated TX_D1) must be a twisted pair. The first bi-directional pair (designated BI_D3) must be a twisted pair and the second bi-directional pair (designated BI_D4) must be a twisted pair. Category 3, 4 or 5 cable may be used.

Link Integrity
There are LEDs on the adapters that show link integrity:

  • A LNK light for link
  • An ACT light for activity
  • A 100 light which indicates a 100 MBPS connection

Some models use one LED to show both link and activity.

Refer to your adapter Installation Guide or the "Diagnostic LEDs" Readme file for complete information.

Note The ACT LED indicates read/write activity on the network, not necessarily activity on the adapter.

Common Problems

Problem: A hub can't detect a workstation.

Solution: This is often the result of a crossed wire in the cable or wiring closet. You should have a link light on both the hub and the adapter. Make sure the wiring is correct.

Problem: Workstations can't connect to the network at 100 MBPS but can at 10 MBPS.

Solution: This is most commonly caused by the signals being split over pairs. Visually check the cable ends for matched color pairs. Pins 1&2 should be a matched pair, and pins 3&6 should be a matched pair. See Important Cabling Basics above.

Polarity Problems
A common problem in 10BASE-T wiring is crossing the positive and negative phases of the transmit or receive signals (for example, crossing pins 1 (TX+) and 2 (TX-)).

Intel PRO/100 adapters automatically detect this problem and adjust for it internally. However, it's best to check your wiring and correct this problem if you find it.

This applies to:

Intel® PRO/100 CardBus Adapter
Intel® PRO/100 CardBus II Adapter
Intel® PRO/100 Intelligent Server Adapter
Intel® PRO/100 ISA Adapter
Intel® PRO/100 LAN+Modem56 CardBus Adapter
Intel® PRO/100 LAN+Modem56 CardBus II Adapter
Intel® PRO/100 LAN+Modem56 PC Card Adapter
Intel® PRO/100 M Desktop Adapter
Intel® PRO/100 PC Card Adapter
Intel® PRO/100 PCI and EISA Adapters
Intel® PRO/100 S Combo Mobile Adapter
Intel® PRO/100 S Desktop Adapter
Intel® PRO/100 S Dual Port Server Adapter
Intel® PRO/100 S Management Adapter
Intel® PRO/100 S Mobile Adapter
Intel® PRO/100 S Server Adapter
Intel® PRO/100 Smart Adapter
Intel® PRO/100 SR Combo Mobile Adapter
Intel® PRO/100 SR Mobile Adapter
Intel® PRO/100 VE Desktop Adapter
Intel® PRO/100 VM Network Connection
Intel® PRO/100+ Adapter
Intel® PRO/100+ Dual Port Server Adapter
Intel® PRO/100+ Management Adapter
Intel® PRO/100+ Server Adapter
Intel® PRO/100B Adapter
Xircom® 10/100 Network PC Card Adapter (XE2000)
Xircom® 10/100 Network+Modem 56 PC Card Adapter (XEM5600)
Xircom® CardBus Ethernet 10/100 Adapter (CBE-10/100BTX)
Xircom® CardBus Ethernet 10/100+Modem 56 GlobalACCESS Adapter (CBEM56G-100)
Xircom® CardBus Ethernet II 10/100 Adapter (CBE2-100)
Xircom® CreditCard Ethernet 10/100 Adapter (CE3B-100BTX)
Xircom® CreditCard Ethernet 10/100+Modem 56 GlobalACCESS Adapter (CEM56-100)
Xircom® MiniPCI Ethernet 10/100+Modem 56 GlobalACCESS Adapter (MPCI3A56G-100P)
Xircom® RealPort™ CardBus Ethernet 10/100 Adapter (RBE-100)
Xircom® RealPort™ CardBus Ethernet 10/100+Modem 56 GlobalACCESS Adapter (RBEM56G-100)
Xircom® RealPort™ Ethernet 10/100 Adapter (RE-100)
Xircom® RealPort™ Ethernet 10/100+Modem 56 GlobalACCESS Adapter (REM56G-100)
Xircom® RealPort2™ CardBus Ethernet 10/100 Adapter (R2BE-100)
Xircom® RealPort2™ CardBus Ethernet 10/100+Modem 56 GlobalACCESS Adapter (R2BEM56G)
Xircom® RealPort2™ Ethernet 10/100 Adapter (R2E-100BTX)

Solution ID: CS-008464
Last Modified: 20-Apr-2014
Date Created: 18-Jan-2004
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