Interrupt System
C513AO
User’s Manual
7-11
05.99
If two interrupt requests of different priority levels are received simultaneously, the request of higher
priority is serviced. If requests of the same priority are received simultaneously, an internal polling
sequence determines which request is serviced. Thus, within each priority level there is a second
priority structure determined by the polling sequence as shown in Table 7-2.
A low-priority interrupt can be interrupted by a high-priority interrupt, but not by another low-priority
interrupt. A high-priority interrupt cannot be interrupted by any other interrupt source.
Table 7-2
Interrupt Source Structure
Interrupt Source
Priority
External Interrupt 0
Synchronous Serial Channel
Timer 0 Interrupt
External Interrupt 1
Timer 1 Interrupt
Universal Serial Channel
Timer 2 Interrupt
IE0
WCOL OR TC
TFO
IE1
TF1
RI OR TI
TF2 OR EXF2
High
Low
