Fujitsu MB90480 Series Hardware Manual page 67

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Overall flow of interrupt operation
Four types of interrupt functions provide start and return processing, as shown in Figure 3.1-1.
START
Valid hardware
interrupt request
String-type
instruction being
NO
executed*
Fetching and decoding
of next instruction
INT instruction?
NO
RETI instruction?
NO
Execution of normal
instruction
Completed
NO
reiteration of string-type
instruction*
YES
Pointer moved to next
instruction if PC updated
*: When a string-type instruction is being executed, the interrupt condition is checked in each step.
Figure 3.1-1 Overall flow of interrupt operation
Main program
YES
Software
YES interrupt
and exception
processing
Saving dedicated registers
in the system stack
Hardware interrupt
acceptance prohibited
(I = 0)
YES
Execution of
interrupt return
A dedicated register is
returned from the system
stack to the routine that
exists before the interrupt
routine is called.
Interrupt start and return processing
YES
μDMAC?
NO
μDMAC processing
Hardware
YES
interrupt
End of request from
peripheral function?
Saving dedicated registers
in the system stack
Updating CPU interrupt
processing level (ILM)
Reading of interrupt
vector to update PC
and PCB, and then
branching to interrupt
routine
CHAPTER 3 INTERRUPT
μDMAC
Specified count
completed?
NO
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