Defining a functional block – Echelon FTXL User Manual
Page 39
FTXL User’s Guide
27
(for example,
SNVT_volt
), but can be changed during device installation to a
different type (for example,
SNVT_volt_mil
).
Using changeable-type network variables allows you to design a generic device
(such as a generic proportional-integral-derivative (PID) controller) that supports
a wide range of numeric network variable types for set-point, control, and
process-value network variables.
See
Defining a Changeable-Type Network Variable
on page 30 for more
information about implementing changeable-type network variables for FTXL
applications.
You can also define your own nonstandard data types. The NodeBuilder
Resource Editor utility, which is included with the FTXL Development Kit,
allows you to define your own, nonstandard data types for network variables or
configuration properties, and allows definition of your own, nonstandard
functional profiles. These nonstandard types are called user-defined types and
user-defined profiles.
Defining a Functional Block
The first step for defining a device interface is to select the functional profile, or
profiles, that you want your device to implement. You can use the NodeBuilder
Resource Editor to look through the standard functional profiles, as described in
on page 40. You can find detailed documentation for
each of the standard functional profiles
.
For example, if your device is a simple sensor or actuator, you can use one of the
following standard profiles:
• Open-loop sensor (SFPTopenLoopSensor)
• Closed-loop sensor (SFPTclosedLoopSensor)
• Open-loop actuator (SFPTopenLoopActuator)
• Closed-loop actuator (SFPTclosedLoopActuator).
If your device is more complex, look through the other functional profiles to see if
any suitable standard profiles have been defined. If you cannot find an existing
profile that meets your needs, you can define a user functional profile, as
described in
on page 40.
Example: The following example shows a simple functional block declaration.
network output SNVT_amp nvoAmpere;
fblock SFPTopenLoopSensor {
nvoAmpere implements nvoValue;
} fbAmpMeter;
This functional block:
• Is named
fbAmpMeter
(network management tools use this name unless
you include the external_name keyword to define a more human-readable
name)
• Implements the standard profile SFPTopenLoopSensor
2
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