wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

33-2 Industrial Communication Systems
Controller board
Master
station
Local bus
Bus terminal
12.8 km
20 m
400 m
Slave nodes
Remote bus
FIGURE 33.1
Topology flexibility allows a cost-efficient cabling in machines and plants.
inside its local SR. This plug and play function is a great advantage with regard to the installation effort
and service-friendliness of the system. The problems and errors, which may occur when manually
setting device addresses during installation and servicing, are often underestimated.
In order to provide these features, various basic elements must be used in the system as shown in Figure 33.1:
Bus master: The bus master controls all bus operations. It transfers output data to the corresponding
nodes, receives input data, and monitors data transfer. In addition, diagnostic messages are displayed
and error messages are transmitted to the host system. The controller has the responsibility of preparing
the single total frame that provides data distribution among the various nodes.
Remote bus: The controller board is connected to the bus devices via the remote bus. A branch from this
connection is referred to as a remote bus branch. Data can be physically transmitted via copper cables
(RS-485 standard), fiber optics, infrared data links, slip rings, or other media (e.g., wireless). Special bus
terminal modules and certain input/output (I/O) modules or devices such as robots, drives, or operating
devices can be used as remote bus devices. Each one has a local voltage supply and an electrically
isolated outgoing segment. In addition to the data transmission lines, the installation remote bus can
also carry the voltage supply for the connected I/O modules and sensors.
Bus terminal module: The bus terminal modules, or devices with embedded bus terminal module functions,
are connected to the remote bus. The distributed local buses branch out of the bus terminal module
with I/O modules, which establish the interface between INTERBUS and the sensors and actuators.
The bus terminal module divides the system into individual segments, thus enabling to switch individual
branches on/off during operation. The bus terminal module amplifies the data signal (repeater
function) and electrically isolates the bus segments.
Local bus: The local bus branches from the remote bus via a bus coupler and connects the local bus
devices. Branches are not allowed at this level. The communication power is supplied by the bus terminal
module, while the switching voltage for the outputs is applied separately at the output modules.
Local bus devices are typically I/O modules.
33.2 INTERBUS Protocol
INTERBUS operations are based on two cycle types: The identification cycle for system configuration
and error management, and a data transfer cycle for the transmission of user data. Both cycle types are
based on a summation frame whose structure is shown in Figure 33.2.
© 2011 by Taylor and Francis Group, LLC