User guide

156 Additional Features
Table 10. I/O Interrupt Triggers
Trigger Type Example Interrupt Specification
Positive level (default declaration) IO_0
Positive level (explicit declaration) IO_0, +
Negative level IO_0, -
Falling edge IO_0, clockedge(-)
Rising edge IO_0, clockedge(+)
Both rising and falling edge IO_0, clockedge(+-)
Example:
interrupt (IO_0, clockedge(+)) { // rising edge of IO_0
...
}
interrupt (IO_5,-) { // neg. level @ IO_5
...
}
interrupt (IO_6) { // pos. level @ IO_6
...
}
Important: For a single pin, you cannot combine a dual-edge interrupt trigger
(“clockedge(+-)”) with a falling-edge trigger (“clockedge(-)”), because the hardware
would interpret the combination as two dual-edge triggered interrupts. The
Neuron C compiler issues error NCC#586 when it encounters such a
configuration.
Defining a Timer/Counter Interrupt Task
You define a timer/counter interrupt task by referencing a timer/counter I/O
object. Up to two timer/counter interrupt tasks are supported.
Referring to a different I/O model yields compiler error NCC#576, and attempts
to declare more than two timer/counter interrupts yield compiler error NCC#576.
When a timer/counter interrupt task completes, the system firmware clears the
interrupt source, so a when(io_update_occurs()) task cannot process the same
timer/counter update that the interrupt task already processed. You can make
calls to the io_in() function from within the interrupt task, if measurements are
required, and you can share those measurements with the remaining application
through global variables.
The following timer/counter I/O models that are supported as timer/counter
interrupt sources:
• Dualslope Input
• Edgedivide Output
• Edgelog Input
• Frequency Output