Texas Instruments TMS320C645X - Manual (Page 13)

Interrupt and Event Generation
13 General-Purpose Input/Output (GPIO) SPRU724
3 Interrupt and Event Generation
Each GPIO pin (GPn) can be configured to generate a CPU interrupt (GPINTn)
and a synchronization event to the EDMA controller (GPINTn). The interrupt
and EDMA event can be generated on the rising-edge, falling-edge, or on both
edges of the GPIO signal. The edge detection logic is synchronized to the
GPIO peripheral clock.
The direction of the GPIO pin does not need to be input when using the pin to
generate the interrupt and EDMA event. When the GPIO pin is configured as
input, transitions on the pin trigger interrupts and EDMA events. When the
GPIO pin is configured as output, software can toggle the GPIO output register
to change the pin state and in turn trigger the interrupt and EDMA event.
Two internal registers, RIS_TRIG and FAL_TRIG, specify which edge of the
GPn signal generates an interrupt and EDMA event. Each bit in these two
registers corresponds to a GPn pin. Table 1 describes the CPU interrupt and
EDMA event generation of GPn pin based on the bit settings of the RIS_TRIG
and FAL_TRIG registers.
Table 1. GPIO Interrupt and EDMA Event Configuration Options
RIS_TRIG bit n FAL_TRIG bit n CPU Interrupt and EDMA Event Generation
0 0 GPINTn interrupt and EDMA event is disabled
0 1 GPINTn interrupt and EDMA event is triggered on falling edge of GPn
signal
1 0 GPINTn interrupt and EDMA event is triggered on rising edge of GPn
signal
1 1 GPINTn interrupt and EDMA event is triggered on both rising and falling
edge of GPn signal
RIS_TRIG and FAL_TRIG are not directly accessible or visible to the CPU.
These registers are accessed indirectly through four registers:
SET_RIS_TRIG, CLR_RIS_TRIG, SET_FAL_TRIG, and CLR_FAL_TRIG.
Writing 1 to a bit on the SET_RIS_TRIG register sets the corresponding bit on
the RIS_TRIG register. Writing 1 to a bit of CLR_RIS_TRIG register clears the
corresponding bit on the RIS_TRIG register. Writing to SET_FAL_TRIG and
CLR_FAL_TRIG works the same way on the FAL_TRIG register.