Echelon I/O Model Reference for Smart Transceivers and Neuron Chips - Manual (Page 27)

I/O Model Reference 17
io-object-name
A user-supplied name for the I/O object, in the ANSI C format for variable
identifiers.
The description for each I/O object includes a detailed explanation of the syntax
for each I/O model.
Example: A logic level needs to be measured at the IO3 input pin of the device,
which is named IO_3 in Neuron C. The pin is connected to a proximity detector,
as its programmatic name indicates.
IO_3 input bit ioProximity;
Your program can now refer to the IO3 binary input through the ioProximity
variable when using utility functions for this I/O object.
Overlaying I/O Objects
For some I/O models, you can declare more than one I/O object for the same pin.
That is, you can
overlay one I/O object on another.
Example 1: The following declarations allow a program to read four adjacent
pins in one operation (with the nibble I/O model) or read each pin individually
(with the bit I/O model):
IO_4 input nibble ioAllPoints;
IO_4 input bit ioPoint1;
IO_5 input bit ioPoint2;
IO_6 input bit ioPoint3;
IO_7 input bit ioPoint4;
Example 2: The following declarations enable a program to monitor (read back)
the level on its own oneshot output object:
IO_1 output oneshot clock (3) ioBreakHigh;
IO_1 input bit ioBreakHighLevel;
With respect to overlaying, I/O models can be divided into hard pin direction I/O
models and soft pin direction I/O models:
• The soft pin direction I/O models (bit, nibble, and byte) are changed by
subsequent pin declarations. When multiple soft pin direction I/O objects
are declared for the same pin, the last soft I/O object declared is the one
that affects the initial direction of the pin at run-time.
• The hard pin direction I/O models (all other I/O models) are not affected
by subsequent declarations.
The io_set_direction( ) function allows the application to change the direction of
any bit, nibble, or byte type I/O object at run time. See the Neuron C Reference
Guide for information about the io_set_direction( ) function.
In example 2 above, the oneshot model is a hard pin direction I/O model, but the
bit model is a soft pin direction I/O model. The order of declarations is not
important, and the oneshot object is the one that affects the direction of pin IO1
(set during initialization and after reset).
Example 3: If a program declares the following:
IO_2 input bit ioPoint1;
IO_2 output bit ioPoint2;