Image Processing Reference
In-Depth Information
The scheduling information is usually stored in dedicated data structures that are downloaded to
the nodes in the network in order to be available for use by the network management system functions
of the node.
The TTP/A protocol integrates the configuration information for application data flow and the
communication schedule. hus, the local communication schedules (called round descriptor lists) as
well as the interfaces of application services [] are mapped into the same interfacing mechanism,
theIFS(seeSection..).
For the representation of the overall system, the cluster configuration description (CCD) for-
mat was developed that acts as a central and uniform data structure that stores all the information
pertinent to the fieldbus system. his information includes
•
Cluster description meta information: This description block holds information on the
cluster description itself, such as the maintainer, name of the description file, or the
version of the CCD format itself.
•
Communication configuration information: This information includes round sequence
lists as well as round descriptor lists, which represent the detailed specification of the
communication behavior of the cluster. Additionally, this part of the CCD also includes
(partially physical) properties important for communication, such as the universal asyn-
chronous receiver transmitter (UART) specification, line driver, and minimum/maximum
signal run-times.
•
Cluster node information: This block contains information on the nodes in a cluster,
whereas nodes are represented with the STD format.
22.7 Configuration Interfaces
In Section . we focused on the relation between application and configuration. In the following, we
examine parts of system configuration that are mostly independent of the application. We take a short
look on the physical configuration of fieldbus systems, how nodes are recognized by the configuration
system, and how actual application code is downloaded to the fieldbus nodes.
22.7.1 Hardware Configuration
The hardware configuration embraces the setup of plugs and cables of the fieldbus system. Several
fieldbus systems implement means to avoid mistakes, such as connecting a power cable to a sensor
input, which would cause permanent damage to the fieldbus system or even harm people. Moreover,
the hardware configuration interfaces such as plugs and clamps are often subject to failure in harsh
environments, e.g., on a machine that induces a lot of vibration.
For hardware configuration the following approaches can be identified:
•
Usageofspecialjacksandcablesthatsupportatightmechanicalconnectionandavoid
mistakes in orientation and polarity by their geometry.
For example, the actuator-sensor interface
∗
(AS-i) specifies a mechanically coded flat cable that
allows the connection of slaves on any position on the cable by using piercing connectors. AS-i uses
cables with two wires transporting data and energy via the same line. he piercing connectors support
simpleconnection,safecontacting,andprotectionuptoclassIP.
∗
http://www.as-interface.net/.
