UM012811-0904
Interrupts
eZ8 CPU
User Manual
32
Figure 18. Interrupt Vectoring in Program Memory Example
NESTING OF VECTORED INTERRUPTS
Vectored interrupt nesting allows higher priority requests to interrupt a lower priority
request. To initiate vectored interrupt nesting, perform the following steps during the inter-
rupt service routine:
1. Push the old Interrupt Control and Interrupt Enable Register information on the stack.
2. Load the Interrupt Enable Register information with new masks to disable lower
priority interrupts.
3. Execute an EI instruction to enable the interrupts.
4. Proceed with the interrupt service routine processing.
5. After processing is complete, execute a DI instruction to disable the interrupts.
6. Restore the Interrupt Control and Interrupt Enable Register information from the
stack.
7. Execute an IRET instruction to return from the interrupt service routine.
Program Memory
Vector Selected by
Interrupt Controller
Interrupt
Vector
Table
Interrupt Service
Routine Origin
Vector[15:8] = 45H
Vector[7:0] = 67H
4567H
Program Memory
Address
0014H
0015H
