SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
The PIE provides individual flag and enable register bits for each of the peripheral interrupt signals, which are sometimes called PIE channels. These channels are grouped according to the associated CPU interrupt. Each PIE group has one 16-bit enable register (PIEIERx), one 16-bit flag register (PIEIFRx), and one bit in the PIE acknowledge register (PIEACK). The PIEACK register bit acts as a common interrupt mask for the entire PIE group.
When the CPU receives an interrupt, the CPU fetches the address of the ISR from the PIE. The PIE returns the vector for the lowest-numbered channel in the group that is both flagged and enabled. This gives lower-numbered interrupts a higher priority when multiple interrupts are pending.
If no interrupt is both flagged and enabled, the PIE returns the vector for channel 1. This condition does not happen unless software changes the state of the PIE while an interrupt is propagating. Section 3.4.4 contains procedures for safely modifying the PIE configuration once interrupts have been enabled.