D17133CS datasheet(167/289 Pages) NEC

167 / 289 page

CHAPTER 14

INTERRUPT FUNCTIONS

152

14.3 INTERRUPT SEQUENCE

14.3.1 Acceptance of Interrupts

The moment an interrupt is accepted, the instruction cycle of the instruction which has been executed is

terminated, and the interrupt operation is started thus altering the flow of the program to the vector address.

However, if the interrupt occurs during execution of the MOVT instruction, the EI instruction or an instruction which

has satisfied the skip condition, the processing of this interrupt is started after two instruction cycles are completed.

If interrupt operation is started, one level of the address stack register is consumed to store the return address

of the program, and also a level of the interrupt stack register is used to save the PSWORD in the system register.

If multiple interrupts are enabled and occure simultaneously, the interrupts are processed in order of higher priority.

In this case, an interrupt with a lower priority is put on hold until the interrupts with higher priority are processed.

For details of the priority levels, refer to Table 14-1. Types of Interrupt Factors.

Caution The PSWORD is automatically reset to 00000B after being saved in the interrupt stack register.

D17133CS Datasheet(PDF) 167 Page - NEC