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CHAPTER 8 INTERRUPT CONTROLLER
Example of interrupt routines
The above example indicates that a priority inter rupt is caused during execution of interrupt
routine I. In this case, incrementing PDRR at the begin ning of each interrupt routine and
decrementing it at the exit of each routine can also prevent a hold request from being issued
accidentally.
<Notes>
Always in crem ent PDR R at t he begi nning of th e in terrupt routine to be ex ecuted dur ing DM A
transfer (in CPU hold state) and decrement it at the exit of the routine to prevent DMA
transfer during execution of the interrupt routine.
On the o ther hand, incrementing or decrementing PDRR during e xecution of an ordinary
interrupt routine prevents DMA transfer during execution of the interrupt routine and may
deteriorate performance.
Carefull y note the relationship between the interrupt levels set in the HRCL and the ICR
registers.
Incrementing PDRR
Clearing the interrupt cause
Decrementing PDRR
RETI