SPRUIY2 November 2024 F29H850TU , F29H859TU-Q1
The Realtime Interrupt Stack (RTINT) is a dedicated hardware stack used by the Realtime Interrupt (RTINT) and the Non Maskable Interrupt (NMI). For details on the differences between the various interrupt types, see Chapter 3. When either of these interrupts are triggered, all C29x CPU working registers (Ax, Dx, Mx, RPC, DSTS, and ESTS) and return address are saved on the RTINT stack within 8 cycles and restored in 8 cycles when the RETI.RTINT instruction is executed. Nesting of RTINT is allowed up to the number of levels supported by the Realtime Interrupt Stack minus 1 level, with the NMI interrupt always having one reserved level.
Real Time Interrupt stack pointer (RTISP) register: The RTISP register keeps track of the utilization of stack and shows the current value of Real Time Interrupt stack pointer. This register is automatically incremented by hardware when Real Time Interrupt or NMI interrupt is triggered and decremented when RETI.RTINT instruction is executed.
Warning level for Real Time Interrupt stack pointer (WARNISP) register: This WARNISP is a user configurable register which allows early warning of real time interrupt stack overflow detection, when RTISP register is greater than or equal to WARNISP register value.
Maximum Real Time Interrupt Stack Pointer (MAXISP) register: The MAXISP register is not user configurable register. When ISP register equals to MAXISP register, CPU enters fault state as real time interrupt stack is full.
For more details on registers related to the Real Time Interrupt stack, see Section 3.4.3.