Page 344 - Programmable Logic Controllers, Fifth Edition - Mobile version

detect an object. A limit switch can report the number of
motions it has performed, which may be an indication It allows users to link information seamlessly between
devices running the EtherNet/IP protocol without custom
that it has reached the end of its operating life and thus hardware, as illustrated in Figure 14-42.
requires replacement. The following are some of the important features of
EtherNet/IP:
ControlNet
ControlNet is positioned one level above DeviceNet. It • Sharing a common application layer between
uses the Common Industrial Protocol (CIP) to combine ControlNet, DeviceNet, and Ethernet/IP will make
the functionality of an I/O network and a peer-to-peer plug-and-play interoperability possible among com-
network providing high-speed performance for both func- plex devices from multiple vendors. Plug and play
tions. This open high-speed network is highly determin- refers to the ability of a computer system to auto-
istic and repeatable. Determinism is the ability to reliably matically configure devices. This allows you to plug
predict when data will be delivered, and repeatability in a device and play (operate) it without worrying
ensures that transmit times are constant and unaffected by about setting DIP switches, jumpers, and other con-
devices connecting to, or leaving, the network. Electronic figuration elements.
device data sheets (EDS-Files) are required for each • EtherNet/IP provides standardized full-duplex
ControlNet device. During the setup phase the ControlNet operation which gives a single node, in a peer-
scanner must configure each device according to the EDS- to-peer connection, full attention and therefore
Files. The ControlNet layout shown in Figure 14-41 has a maximum possible bandwidth. Bandwidth refers
redundant media option in which two separate cables are to the data rate supported by a network, com-
installed to guard against failures such as cut cables, loose monly expressed in terms of bits per second.
connectors, or noise. The greater the bandwidth the greater the overall
performance.
EtherNet/IP • EtherNet/IP allows interoperability of industrial
EtherNet/IP (Ethernet Industrial Protocol) is an open automation devices and control equipment on the
communications protocol based on the Common Industrial same network used for business applications and
Protocol (CIP) layer used in both DeviceNet and ControlNet. browsing the Internet.

ControlNet
scanner

A
B

Redundant media

Figure 14-41 ControlNet network with redundant media installed.

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