Ethernet Bus

Ethernet Baseband Network Standard
IEEE 802.3


[Ethernet Description] [Ethernet Interface ICs]
[Ethernet Connectors] [Ethernet Pin-Out] [OnLine Standards]
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Ethernet Description

The Ethernet interface is a cable bus which runs over copper or fiber. The copper interfaces use either a coax line or differential twisted pairs, while the fiber runs use fiber-optic cables. The Ethernet network is defined by IEEE 802.3. Descriptions for each of the physical lines are provided below. In addition to normal Ethernet signalling IEEE 802.3af defines unused lines which supply DC power to peripheral devices. IEEE 802.3af, or Power Over Ethernet is described on the POE interface page. IEEE 802.3ah, or Ethernet in the First Mile on the EFM interface page.

The Ethernet standard uses Manchester Encoding and Decoding. Access control is gained via Carrier Sense, Multiple Access with Collision Detect (CSMA_CD). Preamble Field: A 56 bit pattern of alternating ones and zeros which are used to synchronize the receiver clock to the incoming data packet. SFD Field: Start Frame Delimiter Field, indicates the beginning of the frame; [10101011].


Ethernet Frame Packet
Ethernet Packet




10Base2, or Thin-net Ethernet has the capability to run at 10M bits/sec. [+/-0.01%] for transmission over BNC cables which form the Ethernet architecture, for a distance up to 183 meters. The devices belonging to this subsystem require interconnection via BNC connectors and Coaxial cables (~RG-58), and must conform to IEEE802 specification. The cable shall have a characteristic impedance of 50 ohms +/- 2 ohms. Normally device to device interconnection is handled via 'T' connectors at each device (with no interconnecting cable between the 'T' and the logical device). Each device should be separated by 0.5 meters minimum. BNC 50 ohm terminators are used (on the opposite end) at the end of each end of the chain. The total number of device on a single chain is 30, normally configured in a linear configuration.

10Base2 RG58 / RG59 Cable Diagram


10Base5, or Thick-net Ethernet has the capability to run at 10M bits/sec. [+/-0.01%] for transmission over BNC cables which form the Ethernet architecture, for a distance up to 500 meters. The devices belonging to this subsystem require interconnection via BNC connectors and Coaxial cables (~RG-8), and must conform to IEEE802 specification. The cable shall have a characteristic impedance of 50 ohms +/- 2 ohms. Normally device to device interconnection is handled via 'AUI' connectors at each device. Each device should be separated by 2.5 meters minimum. BNC 50 ohm terminator are used (on the opposite end) at the end of each end of the chain. One side of the chain must have its termination resistor grounded. The total number of devices on a single chain is 100.

10BaseT and [100BaseTX] has the capability to run at 10M bits/sec. [100M bits/sec.] for transmission over Shielded Twisted Pair (STP) cables or Un-shielded Twisted Pair (UTP) (100 ohm) cable which forms the Ethernet architecture. The devices belonging to this subsystem require interconnection via RJ45-type connectors and twisted pair cables (28 AWG minimum), and must conform to IEEE802 specification. This interconnect is point-to-point, commonly in a star topology. Normally this runs out to 100 meters. Normally configured in a star configuration. 10BaseT at a minimum uses "Category 3". 100BaseTX at a minimum uses "Category 5" minimum. The [nominally] 100 ohm cable impedance should be between 85 and 115 ohms and have at least 2 twists per foot. The total number of devices on a single chain is 2. 100Base-TX uses 2 pairs of Cat5 UTP or 2 pairs of 150 ohm shielded balanced cable as defined by ISO/IEC 11801. With 100Base-TX one wire pair is used for transmission, the other pair for collision detection. 100Base-T4 uses of 4 pairs of Cat. 3, 4, or 5 UTP in a star topology at a maximum distance of 100 meters per segment on RJ45 connectors 25Mbps per wire pair].

10BaseF has the capability to run at 10M bits/sec. for transmission over Fiber Optic cable which forms the Ethernet architecture. The devices belonging to this subsystem require interconnection via fiber-type connectors and fiber cables, and must conform to IEEE802 specification. This interconnect is point -to-point. Normally this runs out to 1000 meters.
The table below lists some of the other types. The total number of devices on a single chain is 2. 100Base-FX uses two strands of Multimode Optical Fiber (62.5/125). One strand for transmit and the other strand for receive with a maximum distance of 412 meters per segment in a star topology.

100BaseT Ethernet 100M bits/sec over twisted pair cable. 100BaseT4 / T2 (Cat3 cabling).

Gigabit Ethernet uses either STP copper, UTP [CAT-5] copper, or fiber. The interface uses the Gigabit Interface Converter [GBIC]. The fiber versions may be called: 10Gbase-mc. Operates over fiber using one of three wavelengths; 850nm, 1300nm, or 1550nm. 'm' determines the wavelength, 'c' determines the coding.

1000BaseKx --
1000BaseSx Operates over fiber using a wavelength of 780nm, maximum fiber length is 500 meters

1000BaseLx Operates over fiber using a wavelength of 1300nm, maximum fiber length is 3 km

1000BaseCX [10Gbase-T] 10 Gigabit/sec PHY Ethernet standard for twisted pair cabling. The cabling may be [CAT-6] copper wiring, to 55 meters, or [CAT-7] copper wiring, to 100 meters. 10 Gigabit Ethernet only supports full duplex operation. Impedance is 150 ohms.

1000Base-T. [Gigabit Ethernet] operates up to 100 meters on EIA568, 4-pair [CAT-5] UTP [Un-Shielded Twisted Pair] 100 ohm copper wiring. This is backwards compatible with 100Base-T. Also uses Fibre Channel as the physical layer, and runs at 1000Mbps, using 8B/10B encoding.

Ethernet Major Formats
Protocol Frequency Distance Cable
-- MHz Meter --
10Base-2 10 183 Coax
10Base-5 10 500 Coax
10Base-T 10 100 STP/UTP
10Base-F 10 1000 Fiber
100Base-T 100 100 STP/UTP
100Base-T4 100 100 STP/UTP
100Base-TX 100 100 STP/UTP
100Base-FX 100 -- Fiber

The nomenclature used in xBasex refers to the following:
10Base"X"; the 'X' refers to ~distance, 2 for 200 meters (actually 183 meters), 5 for 500 meters, T for Twisted pair, F for Fiber.
The "10" (the first number) refers to speed. The 10 refers to 10MHz, the 100 refers to 100MHz.

The frame check sequence is derived from a Cyclic Redundancy Code (CRC); the coefficients are generated modulo-2:
X31 + X26 + X23 + X22 + X16 + X12 + X11 + X10 + X8 + X7 + X5 + X4 +X2 + X + 1

{Ethernet Interface Bus Index}


Ethernet Bus 10BaseT Pin-Out

Ethernet 10BaseT (Twisted Pair)
Pin # Signal Name Function
1 TD+ Transmit Data
2 TD- Transmit Data
3 RD+ Receive Data
4 NC No Connection
5 NC No Connection
6 RD- Receive Data
7 NC No Connection
8 NC No Connection

Refer to the AUI Pinout page for the pin out of the AUI connector.

{Ethernet Interface Bus Index}





Ethernet Bus Interface IC Manufacturers

Broadcom Corporation {Gigabit Ethernet chips; Controllers / transceivers}

Cirrus Logic {10/100 Mbps Ethernet transceiver-quad 10BASE-T transceiver}

Davicom Semiconductor Inc. {Gigabit Ethernet Chipsets}

Freescale Semiconductor, Inc. {Ethernet Transceiver}

Fujitsu Microelectronics Inc. {10/100 Ethernet Controller-Bridge Controller-10Base-T Interface/Transceiver}

Integrated Device Technology, Inc. 'IDT' {Fast Ethernet: 100 Mbits/s full/half duplex ICs, 10Base-T/100Base-TX Integrated PHYceiver}

Intel {Gigabit-Fast10/100 Quad Transceiver/Repeater-10Base-T Transceiver/Adaptor-Media Access Controller (MAC)}

LSI Corporation {10/100 Ethernet Controller/MAC-Ethernet Controllers}

Marvell Technology Group Ltd. {Fast Ethernet switches, Gigabit Ethernet transceiver, 10/100 and 10/100/1000Mbps Ethernet controllers}

Micrel Semiconductor {10/100 Switch-PHY}

National Semiconductor {10/100Mbit's Ethernet IC Manufacturer}

NXP {Coaxial Ethernet transceiver ICs}

PMC-Sierra Inc. {EXACT chip set-Switch products/10BASE-T}

Realtek Semiconductor Corp. {10/100M Ethernet controller, Unmanaged 10/100M Fast Ethernet switch controllers}

Standard Microsystems Corp. 'SMSC' {10 Mbps and 100 Mbps Ethernet Controllers and Transceivers}

TI {Ethernet Switch IC}

Triquint Semiconductor {Gbaud Fibre-Channel/Gbit Ethernet Transmitter/Receiver/Transceiver ICs}

Vitesse Semiconductor Corp. {Gbit Ethernet IC Manufacturer}

Zarlink Semiconductor {Managed / Unmanaged Ethernet Switches, Fast/Gigabit Ethernet}

IC Manufacturer {All other functions}


10Base2 / 10BaseT Ethernet Characteristics
Signal Type 10Base2 Characteristics 10BaseT Characteristics
Output Voltage (High) VOH= - 0.225 volts VOH= + 0.700 volts
Output Voltage (Low) VOL= - 1.825 volts VOL= - 0.700 volts
Output Current; AC +/- 16mA; 14mA min., 19mA max. TBD
Output Current; DC +/- 4.5mA; 4mA min., 5mA max. N/A, AC Signal
Output Impedance Greater then 50k ohms Greater then 50k ohm
Circuit Type ECL [Emitter Coupled Logic] ECL, Balanced differential
Level Transition Time 25nS +/-5nS @ 10% to 90% 25nS +/-5nS @ 10% to 90%
Encoding Format Manchester Phase Encoding Manchester Phase Encoding
Transmit / Receive Frequency. 10Mbps +/- 0.01% 10Mbps +/- 0.01%
Topology Branching Bus Chained Bus
Medium Shielded Coaxial Cable 15 pin Shielded Multi-Conductor
Access Control Carrier Sense, Multiple Access with Collision, CSMA/CD CSMA/CD

{Ethernet Bus Index}


Ethernet Online Standards Information

ANSI/IEEE 802.3 and ISO/IEC 8802-3

Institute of Electrical and Electronics Engineers, Inc., IEEE, http://www.ieee.org/

{Ethernet Bus Index}


Ethernet Bus Connector Vendors




Gigabit Ethernet HSSDC (High Speed Serial Data Connector) Connector/Cable; 2mm Twin-ax

Erni {Gigabit Ethernet}

JDS UNIPHASE {Multi-mode 850nM/Single-mode 1310nm GigaBit transcevers}

Methode Electronics Inc {Unshielded Twisted Pair (UTP) / Glass Optical Fiber (GOF) for Ethernet, Fast/Gigabit Ethernet}

Samtec {IP68 ethernet cable plug, circular, panel adapter}

Tyco Electronics {Coax-BNC-Gigabit Ethernet Connector Manufacturer}

Refer to this page for Industrial Ethernet Connectors; for harsh environments: Reinforced, Water proof, Military.

Connector Manufacturer Listing

{Ethernet Bus Index}


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Modified 2/26/12
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