Echelon Neuron C - Manual (Page 124)

104 Functions
cannot specify TCCLK_40MHz or TCCLK_20MHz – no
error is issued, but the effective value used in this case is
TCCLK_10MHz).
Example
IO_1 output pulsecount clock(3) pcout;
when(...)
{
io_set_clock(pcout, 5);
// equivalent to io_set_clock(pcout, TCCLK_156k2Hz);
...
}
io_set_direction( ) Built-in Function
The io_set_direction( ) built-in function allows the application to change the
direction of any bit, nibble, or byte type I/O pin at runtime. The
dir parameter is
optional. If not provided, io_set_direction( ) sets the direction based on the
direction specified in the declaration of
io-object-name .
A program can define multiple types of I/O objects for a single pin. When
directions conflict and a timer/counter object is defined, the direction of the
timer/counter object is used, regardless of the order of definition. However, if the
program uses the io_set_direction( ) function for such an object, the direction is
changed as specified.
To change the direction of overlaid I/O objects, at least one of the objects must be
one of the allowed types for io_set_direction( ) and that I/O object must be used to
change directions, even if the subsequent I/O object used is a different one.
For example, if you overlaid a bit input with a oneshot output, you only can use
the bit I/O object with io_set_direction( ) to change the direction from input to
output, thus enabling the oneshot output.
Any io_changes events requested for input objects can trigger when the object is
redirected as an output, because the Neuron firmware returns the last value
output on an output object as the input value. Thus, the user might want to
qualify io_changes events with flags maintained by the program to indicate the
current direction of the device.
Syntax
typedef enum {IO_DIR_IN=0, IO_DIR_OUT=1} io_direction;
void io_set_direction ( io-object-name , [io_direction dir ]);
io-object-name The I/O object name that corresponds to io-object-name in
the I/O declaration. This built-in function is used only for
direct I/O objects such as bit, nibble, and byte.
dir An optional direction, using a value from the io_direction
enum shown above. If omitted, uses the declared
direction of the I/O device to set the pin direction.