INTERRUPTS
6.9 Multiple interrupts
Interrupt request
generated
Nesting
Reset
Main routine
I = 1
Time
IPL = 0
I = 0
Interrupt 1
Interrupt priority level = 3
Interrupt 1
I = 1
IPL = 3
I = 0
Multiple interrupts
Interrupt 2
Interrupt priority level = 5
Interrupt 2
I = 1
IPL = 5
Interrupt 3
RTI
Interrupt priority level = 2
I = 0
IPL = 3
Interrupt 3
RTI
This request cannot be accepted
because its priority level is lower
than the interrupt 1’s one.
I = 0
IPL = 0
The instruction in the main routine is
not executed.
Interrupt 3
I = 1
IPL = 2
RTI
I = 0
I : Interrupt disable flag
IPL = 0
IPL : Processor interrupt priority level
: They are automatically executed.
: They must be set by software.
Fig. 6.9.1 Processing for multiple interrupts
7906 Group User’s Manual Rev.2.0
6-17
RENESAS [ RENESAS TECHNOLOGY CORP ]
