Topic RJ45SPEC from HARDW FAQ base
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TPE cabling specifications Specifications and recommendations for Twisted-Pair Ethernet cable ================================================================== The EtherExpress(TM) PRO/10 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. This document covers the following topics: - Recommended cables - Cable and connector pinouts - Connecting two workstations without a hub - Link integrity - Common problems For more information on the 10BASE-T specification, contact your local network supplier or call the IEEE (800-678-IEEE). Recommended cables ================== The RJ45 connector can use 22, 24, or 26-gauge UTP cabling. The cable must comply with the IEEE 802.3 10BASE-T standard. If you're using TPE cabling in an residential environment, you must use a shielded cable. The cable between the computer and the hub must be less than 100 meters long. If the inter-repeater link distance is more than 300m, please insert "Stop backoff on CRS 0" as a command line parameter in the net.cfg file. These UTP cables work well: ------------------------------------------------------ Manufacturer Model number No. of pairs ------------------------------------------------------ Belden 9562 2 ------------------------------------------------------ Data Set 2402 4 ------------------------------------------------------ Belden 9566 6 ------------------------------------------------------ Silver satin is not within the 10BASE-T specification and cannot be used. If used, it may not work at all, or may give intermittent results. The EtherExpress adapters do not support pre10BASE-T concentrators. 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. Use only four of the eight pins. Pins 1 and 2 must be a pair, and pins 3 and six must be a pair. Function Pin# Pin# ------------------------------------- TX+ 1 <--------> 1 TX- 2 <--------> 2 RX+ 3 <--------> 3 RX- 6 <--------> 6 ------------------------------------- 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 ----------------------------- ---------- -------------------------- 1 |-- | 8 |------------ | 2 |-- | 7 |------------ | 3 |-- --- 6 |------------ | 4 |-- | 5 |------------ | 5 |-- | 4 |------------ | 6 |-- --- 3 |------------ | 7 |-- | 2 |------------ | 8 |-- | 1 |------------ | ---------- -------------------------- END TOP Pin name and function: 1 Transmit Data Plus. The positive signal for the TD differential pair. This signal contains the serial output data stream transmitted onto the network. 2 Transmit Data Minus. The negative signal for the TD differential pair. This contains the same output as pin 1. 3 Receive Data Plus. The positive signal for the RD differential pair. This signal contains the serial input data stream received from the network. 4 not connected 5 not connected 6 Receive data minus. The negative signal for the RD differential pair. This signal contains the same input as pin 3. 7 not connected 8 not connected Connecting two workstations without a hub ========================================= 10BASE-T uses a star topology. This means there is a hub or concentrator 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 requires a special cable that incorporates the crossover function talked about at the beginning of this document. Function Pin# Pin# Function -------------------------------------------------- TX+ 1 <--------> 3 RX+ TX- 2 <--------> 6 RX- RX+ 3 <--------> 1 TX+ RX- 6 <--------> 2 TX- -------------------------------------------------- NOTE: This is not an IEEE supported configuration and should be used for test purposes only. Link integrity ============== For 10BASE-T networks, Link integrity (LI) needs to be on. Some transceivers, Ethernet cards, or other network devices allow you to turn it off, but Link Integrity is always on with the EtherExpress adapters. If you're using a transceiver to go to a thick/thin Ethernet segment, Link Integrity must be set to on for the transceiver. Common problems =============== A hub can't "see" a workstation ------------------------------- This is often caused by a crossed wire in the cable or wiring closet. Check to make sure the wiring is correct. Workstations can't connect to the network ----------------------------------------- If your workstations are having problems connecting, reset or power off/on your concentrator or hub. Polarity problems ----------------- A common problem in 10BASE-T wiring is crossing the positive and negative phases of the transmit or receive signals. For example, a problem would occur if pins 1 and 2 were crossed. (TX+ connected to TX-). The current EtherExpress adapters automatically detect this problem and adjust for it internally. Early EtherExpress 16TP's did not have this feature. Even though the current EtherExpress adapters can take care of this crossover for you, it is best to check your wiring and correct this problem if you find it.
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