Ethernet Address (Mac-Id); Ethernet Packet; Channel Access Method - WAGO 750 Series Manual

5.3.2.1 ETHERNET

ETHERNET address (MAC-ID)

Each WAGO ETHERNET fieldbus coupler is provided from the factory with
a unique and internationally unambiguous physical ETHERNET address, also
referred to as MAC-ID (Media Access Control Identity). This can be used by
the network operating system for addressing on a hardware level.
The address has a fixed length of 6 Bytes (48 Bit) and contains the address
type, the manufacturer's ID, and the serial number.
Examples for the MAC-ID of a WAGO ETHERNET fieldbus coupler
(hexadecimal): 00
ETHERNET does not allow addressing of different networks.
If an ETHERNET network is to be connected to other networks, higher-
ranking protocols have to be used.
Note
If you wish to connect one or more data networks, routers have to be
used.

ETHERNET Packet

The datagrams exchanged on the transmission medium are called
"ETHERNET packets" or just "packets". Transmission is connectionless; i.e.
the sender does not receive any feedback from the receiver. The data used is
packed in an address information frame. The following figure shows the
structure of such a packet.
Preamble
8 Byte
Fig. 5-9: ETHERNET-Packet
The preamble serves as a synchronization between the transmitting station and
the receiving station. The ETHERNET header contains the MAC addresses of
the transmitter and the receiver, and a type field.
The type field is used to identify the following protocol by way of
unambiguous coding (e.g., 0800

5.3.3 Channel access method

In the ETHERNET Standard, the fieldbus node accesses the bus using
CSMA/CD (Carrier Sense Multiple Access/ Collision Detection).
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Each station can send a message once it has established that the transmission
medium is free. If collisions of data packets occur due to several stations
transmitting simultaneously, CSMA/CD ensures that these are detected and
the data transmission is repeated.
However, this does not make data transmission reliable enough for industrial
requirements. To ensure that communication and data transmission via
ETHERNET is reliable, various communication protocols are required.
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP
30
H- H-
ETHERNET-Header
14 Byte
Carrier Sense:
Multiple Access:
Collision Detection: A collision is detected.
DE 00 00 01
H- H- H- H.
ETHERNET_Data
46-1500 Byte
= Internet Protocol).
hex
The transmitter senses the bus.
Several transmitters can access the bus.
ETHERNET
Network Communication
Check sum
4 Byte
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