Siemens SIMATIC NET Operations Instructions download pdf (Page 17)

Industrial Ethernet Networks

2-3

SIMATIC NET Twisted-Pair and Fiber-Optic Networks

C79000-G8976-C125-02

2.1 Ethernet Standard IEEE 802.3

IEEE Standard 802.3

The international “Institute of Electrical and Electronic Engineers (IEEE)” specified

the first Ethernet standard 10BASE5 /1/ in 1985. This standard based on coaxial

cable as the transmission medium was the basis for the first Industrial Ethernet.

Under the name SINEC H1, this network, enhanced by the introduction of a triaxial

cable, has proved itself for many years in process and manufacturing automation

/6/.

From the very beginning, both the IEEE standard and the SIMATIC NET range of

products have constantly been improved and expanded, further increasing the

flexibility and performance of Ethernet networks. These expansions and

improvements include, for example, the introduction of transmission on fiber-optic

cables and twisted-pair cables and the introduction of Fast Ethernet increasing the

transmission rate by a factor of 10.

The common basis of all these Ethernet versions is baseband signaling and the

CSMA/CD medium access protocol.

Baseband Signaling

According to IEEE 802.3, Ethernet uses the baseband signaling technique. This

means that data is transmitted unmodulated in pulse form on the transmission

medium (for example bus cable). The transmission medium forms a single

transmission channel whose capacity must be shared by the attached DTEs. All

attached DTEs receive the data transmitted on the medium at the same time. At

any one time, only one single DTE is permitted to send data. If more than one DTE

sends data at the same time, a collision occurs on the transmission medium. The

data signals of the DTEs attempting to transmit destroy each other.

Coordinated access to the common transmission medium is obviously necessary.

The IEEE 802.3 standard solves this problem using the CSMA/CD protocol.

1 ... 16 17 18 ... 338

No comments

Siemens SIMATIC NET Operations Instructions Page 17