Echelon Mini FX - Manual (Page 79)

66 Developing Device Applications
Timers may be automatically reloading (repeating), or one-shot timers, with a duration
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 type, clock speed, and other factors (see the I/O Model
Reference for more information). The Series 5000 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.
Neuron C Variables
The following sections briefly discuss various aspects of Neuron C-specific variable
declarations. Data types affect what sort of data a variable represents. Storage
classes affect where the variable is stored, whether it can be modified (and if so, how
often), and whether there are any device interface aspects to modifying the data.
Neuron C Variable Types
Neuron C supports the following C variable types. The keywords shown in square
brackets below are optional. If omitted, they will be assumed by the Neuron C
language, per the rules of the ANSI C standard:
• [signed] long [int] 16-bit
quantity
• unsigned long [int] 16-bit quantity
• signed char 8-bit quantity
• [unsigned] char 8-bit quantity
• [signed] [short][int] 8-bit quantity
• unsigned [short][int] 8-bit quantity
• enum 8-bit quantity (int type)
Neuron C provides some predefined enum types. One example is shown below:
typedef enum {FALSE, TRUE} boolean;
You should use the unsigned int type whenever possible because it is the type best
supported by the Neuron Chip and Smart Transceiver’s hardware architecture. The
unsigned int type is preferred over signed int type.
Neuron C also provides predefined objects that, in many ways, provide the look and feel
of an ANSI C language variable. These objects include Neuron C timer and I/O objects.
See Chapter 2 of the Neuron C Programmer’s Guide for more details on I/O objects, and
see Chapter 4 in the Neuron C Reference Guide for more details on timer objects.
The extended arithmetic library also defines float_type and s32_type for IEEE 754 and
signed 32.bit integer data respectively. These types are detailed further in Chapter 3 of
the Neuron C Reference Guide.