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MB86R02 ‘Jade-D’ Hardware Manual V1.64
9.6.3 Multiple interrupt processing
The example of executing the multiple interrupt processing is shown.
Main routine
IRQ request 1
→
The first interrupt process
(1) Save the register value in the stack.
(2) Save a present ILM register value and SPSR_irq
(existence in the core) register value in the stack.
Do not lose by the following interrupt process.
(3) Set the value of the ICRMN register to the ILM register,
and interrupt effectively at a level that is higher than the
first interruption.
(4) The interruption source that is occurring currently is clear.
(5) The IRQF flag is clear (NIRQ is negated, and the decision
of the interruption level restarts).
(6) Confirm the clearness of the IRQ flag.
(7) Clear I bit to the CPSR register in the ARM7TDMI core
and enable the interruption reception.
IRQ request 2
→
The first interrupt return process
Do the same interrupt return process
as the second to the first interruption.
The second interruption process
Do the same interrupt process as
the first to the second interruption.
The second interruption return process
(1) Set I bit of the CPSR register, and
disable the interruption.
(2) Restore the value of SPSR_irq saved
in the stack to the SPSR_irq register.
(3) Restore the value in the stack to the
register.
(4) Restore the PC value to return to former
routine, and restore the SPSR_irq
register value to the CPSR register.
CPSR
→
SPSR_irq
Figure 9-3 Multiple IRQ interrupt processing example
9.6.4 Example of IRQ interrupt handler
IRQ_Handler ROUT
STMFD SP!, {R0-R12, R14}
;The register value is preserved.
MESSAGE "Enter Dummy IRQ Handler"
LDR
R0, = ILM
LDR
R1, [R0]
MRS
R2, SPSR
STMFD
SP!, {R1, R2}
;Preserve the value of ILM and the SPSR_irq register.
LDR
R2, = ICRMN
LDR
R1, [R2]
STR
R1, [R0]
;Set the ICRMN register value to the ILM register.
Summary of Contents for MB86R02
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