A SERVICE OF

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8XC196MC, MD, MH USER’S MANUAL
5-8
The interrupt service routine should read the PI_PEND (Figure 5-12 on page 5-23) register to de-
termine the source of the interrupt. Before executing the return instruction, the interrupt service
routine should check to see if any of the other interrupt sources are pending. Generally, PTS in-
terrupt service is not useful for multiplexed interrupts because the PTS cannot readily determine
the interrupt source.
Figure 5-3. Flow Diagram for the OVRTM Interrupt
A3254-01
Set OVRTM
x
bit in PI_PEND
Is OVRTM
x
bit set in
PI_MASK
?
Yes
No
Timer
x
Overflows
Set OVRTM
bit in INT_PEND
OVRTM bit
is not set
in INT_PEND
Is OVRTM
bit set in
INT_MASK
?
Yes
No
OVRTM interrupt
is not generated
Generate
OVRTM interrupt
Read PI_PEND
to see which
timer overflowed