ICC DNET-100, User Manual

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12. Point Configuration
As mentioned in section 1, the Network Gateway Series concept revolves
around a central “point database”, containing various individual points. A
“point” is simply an object that defines some sort of primary -to- secondary
network mapping information. In the case of the DNET-100, a point is simply a
DeviceNet parameter object, whose characteristics (attributes) are entered by
the user via the serial console. Throughout the remainder of this manual,
therefore, configured points may also be referenced by their more naturally-
associated terms “parameters”, “parameter objects”, or “DeviceNet
parameters”. Up to a total of 100 individual parameters can be defined, and
they can be allocated as necessary to any secondary-network device and
contained data item.
The information that must be entered by the user to define the characteristics
of a parameter can be divided into two subsets: that information required to
map parameter objects to their appropriate secondary-network device and
contained data item, and that information required to conveniently define and
access the parameter via the DeviceNet network (i.e. to generate an Electronic
Data Sheet (EDS) and access the parameter via a network configuration tool,
such as Rockwell Software’s
RSNetWorx For DeviceNet ).
The required mapping information includes the secondary-network device’s
station number (or ASD port number in the case of an ASD common serial
secondary network), the secondary network data item (register number,
parameter number etc.) residing in that device, and the DeviceNet parameter
object instance (or “parameter number”). The mapping information is required
to provide access to the targeted secondary network data item when the
parameter is accessed via explicit messaging, or when the parameter is
included in one of the available I/O assembly objects and accessed via the
polled or COS/cyclic I/O connections.
The parameter definition information includes such items as the parameter’s
data type, name, help string, minimum, maximum and default values, scaling
factors and decimal precision. Considerations are also included to provide a
parameter-specific timeout value to be written to the parameter’s associated
secondary network object in the event of a DeviceNet network timeout. In
general, parameter definition information has no bearing on the normal
operation of the gateway (i.e. communication with a scanner or other master
device): it exists only to create a customized EDS when configuration is
complete, and to be used by a network configuration tool to facilitate proper
data display and entry methods when accessed via the explicit messaging
connection.