SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
When an interrupt (INT15–INT4, SWI, and UNDEF) is taken, the CSR[0]GIE bit is cleared by the hardware and subsequently the GIE bit is restored on interrupt return via the BIRP instruction. Thus all maskable interrupts (INT15–INT4) are disabled within the interrupt service routine of maskable interrupts.
Also, when an NMI is taken, the IER[1]NMIE bit is cleared by the hardware and subsequently the IER[1]NMIE bit is restored on interrupt return via the BNRP instruction. Thus NMI and all maskable interrupts (INT15–INT4) are disabled within the NMI service routine.
So in general, nesting of interrupts (except the case of NMI within a maskable interrupt routine) is disabled. However, under software control, it is possible that the ARP32 CPU is configured to take fully nested interrupts.
The ARP32 CPU offers two programming models with respect to usage of interrupts in a nested or non-nested manner.