M32C8A Datasheet, PDF (126/372 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M32C/80 Series

M32C/8A Group
11. Interrupts
11.6.7 Returning from Interrupt Routine
When the REIT instruction is executed at the end of an interrupt routine, the values of the FLG register and PC,
which have been saved to the stack before the interrupt sequence is performed, are automatically restored. And
then, the program that was running before an interrupt request was acknowledged, resumes its process. The
high-speed interrupt uses the FREIT instruction instead. Refer to 11.4 High-Speed Interrupt for details.
Before executing the REIT or FREIT instruction, use the POPM instruction or the like to restore registers saved
by program in the interrupt routine. By executing the REIT or FREIT instruction, register bank is switched
back to the bank used immediately before the interrupt sequence.
11.6.8 Interrupt Priority
If two or more interrupt requests are detected at the same sampling points (a timing to detect whether any
interrupt request is generated or not), the interrupt with the highest priority is acknowledged.
Set bits ILVL2 to ILVL0 in the Interrupt Control Register to select the given priority level for maskable
interrupts (peripheral function interrupts).
Priority levels of special interrupts, such as NMI and watchdog timer interrupt are fixed by hardware. Figure
11.9 shows the priority of hardware interrupts.
The interrupt priority does not affect software interrupts. Executing an instruction for a software interrupt
causes the MCU to execute an interrupt routine.
Reset
H
NMI
Watchdog timer
Oscillation stop detection
Vdet4 detection
Peripheral function
Address match
L
Figure 11.9 Interrupt Priority of Hardware Interrupts
11.6.9 Interrupt Priority Level Select Circuit
The interrupt priority level select circuit selects the highest priority interrupt when two or more interrupt
requests are generated at the same sampling point.
Figure 11.10 shows the interrupt priority level select circuit.
Rev.1.00 Jul 15, 2007 Page 109 of 352
REJ09B0385-0100