Automating Manufacturing Systems - Process Control and ...

plc network - 28.15
46 to 1500 bytes in length. The frame concludes with a checksum that will be used to verify
that the data has been transmitted correctly. When the end of the transmission is
detected, the last four bytes are then used to verify that the frame was received correctly.
6 bytes destination address
6 bytes source address
2 bytes ethernet type
46-1500 bytes data
4 bytes checksum
Figure 28.11
Ethernet Version II Frame
28.2.5 Profibus
Another control network that is popular in europe, but also available world wide. It
is also promoted by a consortium of companies (http://www.profibus.com). General features
include;
• A token passing between up to three masters
• Maximum of 126 nodes
• Straight bus topology
• Length from 9600m/9.6Kbps with 7 repeaters to 500m/12Mbps with 4 repeaters
• With fiber optic cable lengths can be over 80Km
• 2 data lines and shield
• Power needed at each station
• Uses RS-485, ethernet, fiber optics, etc.
• 2048 bits of I/O per network frame
28.2.6 Sercos
The SErial Real-time COmmunication System (SERCOS) is an open standard
designed for multi-axis motion control systems. The motion controller and axes can be