Lenze PLC Designer PLC Designer (R3-1) - Manual (Page 112)

L-force | PLC Designer
Concepts and Base Components
110 DMS 4.1 EN 03/2011 TD29
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3.11.1 PLC Configuration
The "PLC Configuration" in »PLC Designer« maps the target system, i.e. the controller
hardware in order to make the I/Os and parameters of the controller and field bus
devices accessible by the application. Further on it allows to monitor the available
device parameters.
The tree of the "PLC Configuration", which in »PLC Designer« V2.3 is handled in own
editor windows, in V3.x is integrated in the device tree, where also the other objects
necessary for running an application on a target system, are arranged. The standard
device editors support the mapping of the current hardware structure into the device
tree by a scan functionality.
The assignment of the I/Os of the PLC to project variables is done either via the "AT
declaration" of a variable in the declaration editor or in the mapping dialog of the
device editor. The device editor provides dialogs for the configuration of a device.
If below a device, which is positioned top-level in the device tree, multiple applications
are inserted, then you can define in the I/O Mapping dialog of the device, which of
those should be regarded for the mapping. When a new PLC gets inserted in the device
tree, primarily per default the application coming with the PLC device will be defined
as "mapping application".
3.11.2 Network topology
The aim is to create a system able to largely configure itself (address assignment), to
support transparently any communication media and to route packets between
different networks. The routing mechanism should be simple enough that any node in
the network, i.e. even nodes with low resources, are able to reroute packets. In
consequence, large routing tables, complex calculations or requests during runtime
should be avoided.
A control network should be configured hierarchically, i.e. each node has one parent
node and an arbitrary number of children. A node without parent is referred to as top-
level node. Cycles are not permitted, i.e. a control network has a tree structure.
Parent-child relationships arise from the specification of network segments. A network
segment corresponds e.g. to a local Ethernet or a serial point-to-point connection. We
distinct between the main network (mainnet) and the sub-networks (subnet). Each
node has at most one main network, wherein it expects its parent, as far as a parent
exists. For each node an arbitrary number of subnets can be configured. The node acts
as parent for all of them.
If a network segment had been defined simultaneously as subnet of several nodes, the
network would have several parents. Though, the resulting configuration will be
invalid, as each network segment is allowed to have one single parent only.