MC81F4x16
11.5 Multi Interrupt
If two requests of different priority levels are received simultaneously, the request of higher priority
level is serviced. If requests of the interrupt are received at the same time simultaneously, an internal
polling sequence determines by hardware which request is serviced. However, multiple processing
through software for special features is possible. Generally when an interrupt is accepted, the I-flag is
cleared to disable any further interrupt. But as user sets I-flag in interrupt routine, some further
interrupt can be serviced even if certain interrupt is in progress.
In this example, the EXT1 interrupt can be
serviced without any pending, even TIMER1 is in
progress.
Because of re-setting the interrupt enable
registers IENH,IENL and master enable “EI” in
the TIMER1 routine.
Figure 11-4 Execution of Multi Interrupt
October 19, 2009 Ver.1.35
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