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CHAPTER 5 INTERRUPT CONTROLLER
5.3
Operation of Interrupt Controller
This section explains operations of interrupt controller including the following.
• Priority evaluation
• Non Maskable interrupt (NMI)
• Hold request cancel/request
• Returning from standby mode (Stop or sleep mode)
■ Priority Evaluation
This module selects the interrupt source of the highest priority from among the interrupt sources occurring
at the same time and outputs the interrupt level and interrupt number of the selected interrupt source to the
CPU.
The criteria for evaluating the priorities of interrupt sources are as follows:
1. NMI
2. Interrupt sources satisfying the following conditions:
• Interrupt sources with an interrupt level value other than 31. ("31" disables interrupts.)
• Interrupt sources with the smallest interrupt level value
• Interrupt source with the smallest interrupt number among above
If any interrupt source is not selected according to the above criteria, the interrupt controller outputs an
interrupt level of 31 (11111
Table 5.3-1 lists interrupt sources, interrupt numbers, and interrupt levels.
120
), where the interrupt number is indeterminate.
B
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