Echelon IzoT NodeBuilder - Manual (Page 189)

Each network variable, configuration property, and functional block is defined by a type definition
contained in a resource file. Network variables and configuration properties are defined by network
variable types (NVTs) and configuration property types (CPTs). Functional blocks are defined by
functional profile templates (FPTs).
Network variables, configuration properties, and functional blocks in Neuron C can use standardized,
interoperable types. The use of standardized data types promotes the interconnection of disparate
devices on a L
ON W ORKS network. For network variables, the standard types are called standard
network variable types (SNVTs). For configuration properties, the standard types are called standard
configuration property types (SCPTs). For functional blocks, the standard types are called standard
functional profile templates (SFPTs). If you cannot find standard types or profiles that meet your
requirements, Neuron C also provides full support for user-defined network variable types (UNVTs),
user-defined configuration property types (UCPTs), and user-defined functional profile templates
(UFPTs).
A Neuron C application executes in the environment provided by the Neuron firmware. This firmware
provides an event-driven scheduling system as part of the Neuron C language’s run-time environment.
Therefore, a Neuron C application does not use a single entry point, as is the case with ANSI C’s
main() function. Instead, a Neuron C application uses when-tasks and interrupt-tasks to specify
application code to be executed in response to various system events or interrupt requests, much in the
way of a .NET event handler.
The Neuron firmware contains a scheduler, which executes these when-tasks in an orderly and
deterministic fashion as and if needed. Neuron C when-tasks can be triggered by system events (such
as reset), network events (such as a network variable update or network error), I/O events (such as a
new reading from an I/O input), timer events, or any arbitrary application-defined event.
Interrupt-tasks are activated as the interrupt request occurs, subject to interrupt prioritization rules.
Neuron C interrupt-tasks can be triggered by edge or level conditions on any of the dedicated I/O pins,
by events occurring in the embedded timer and counter units, or by a dedicated high-resolution system
timer. Interrupt-tasks are only supported by 5000 or 6000 Series chips. Other interrupt sources, such
as those related to sending or transmitting serial data over the embedded UART, are handled
transparently by the Neuron firmware.
Neuron C also provides a lower-level application messaging service integrated into the language in
addition to the network variable model. While the network variable model has the advantage of being
a standardized method of information interchange that promotes interoperability between multiple
devices from multiple vendors, application messaging is available for proprietary and standard
special-purpose solutions. Application messages are used with the L
ON W ORKS file transfer protocol, a
standard mechanism for transfer of large amounts of data, and the ISI protocol, a standard mechanism
to manage networks without intervention of a dedicated tool or specialist.
Another Neuron C data object is the application timer object. Timer objects can be declared and
manipulated like variables. When a timer expires, the Neuron firmware automatically manages the
timer events and notifies the program of those events. Timers may be automatically reloading
(repeating), or one-shot timers, with a resolution ranging from 0.001–65,535 seconds.
Neuron C supports programmable hardware timer units through a variety of I/O library functions.
These functions provide a resolution up to 1 MHz (1 µs) or better, subject to the selected I/O model,
Neuron Chip type, clock speed, and other factors (see the I/O Model Reference for more information).
The 5000 and 6000 Series chips also support a configurable high-resolution system timer, which can
be used to generate periodic interrupt requests.
Neuron C supports up to 35 different I/O models, ranging from simple bit Direct I/O models for typical
input or output hardware to complex Timer/Counter models for triacs. Neuron C also includes Serial
and Parallel I/O models for serial and parallel communication busses. These I/O models are
standardized I/O “device drivers” for the Neuron Chip or Smart Transceiver I/O hardware. Each I/O
model fits into the event-driven programming model. A function-call interface is provided to interact
with each I/O object. The function-call interfaces are optimized for their respective I/O models, yet
they are similar to each other so that they are easy to use.
IzoT NodeBuilder FX User's Guide 175