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3.6 Regarding Interrupts
3.6.1 Types of Interrupt Handlers
MR100's interrupt handlers consist of kernel interrupt handlers and non-kernel interrupt handlers.
The following shows the definition of each type of interrupt handler.
• Kernel interrupt handler
An interrupt handler whose interrupt priority level is lower than a kernel interruption mask level is called kernel
interrupt handler. That is, interruption priority level is from 1 to system_IPL.
A service call can be issued within a kernel interrupt handler. However, interrupt is delayed until it becomes re-
ceivable the kernel interrupt handler generated during service call processing.
• Non-kernel interrupt handler
An interrupt handler whose interrupt priority level is higher than a kernel interrupt mask level is called non-kernel
interrupt handler. That is, interruption priority level is from system_IPL+1 to 7.
A service call cannot be issued within non-kernel interrupt handler. However, the non-kernel interrupt handler is
able to be recieved during service call processing, even if it is the section where it is not able to receive a kernel
interrupt handler:
Figure 3.22 shows the relationship between the non-kernel interrupt handlers and kernel interrupt handlers where the kernel
mask
level is set to 3.
High
Low
0 1 2 3 4 5 6 7
Kernel
Interrupt handler
Non-kernel
Interrupt handler
Kernel mask level
Figure 3.22 Interrupt handler IPLs
3.6.2 The Use of Non-maskable Interrupt
Non-maskable interrupt ( ex. NMI interrupt ,Watchdog Timer interrupt) are treated as a non-kernel interrupt handler.