
Resets and Interrupts
Data Sheet
M68HC11E Family — Rev. 5
96
Resets and Interrupts
MOTOROLA
5.4  Reset and Interrupt Priority 
Resets and interrupts have a hardware priority that determines which reset or 
interrupt is serviced first when simultaneous requests occur. Any maskable 
interrupt can be given priority over other maskable interrupts. 
The first six interrupt sources are not maskable. The priority arrangement for these 
sources is: 
1.
POR or RESET pin 
2.
Clock monitor reset 
3.
COP watchdog reset 
4.
XIRQ interrupt 
5.
Illegal opcode interrupt 
6.
Software interrupt (SWI) 
The maskable interrupt sources have this priority arrangement: 
1.
IRQ 
2.
Real-time interrupt 
3.
Timer input capture 1 
4.
Timer input capture 2 
5.
Timer input capture 3 
6.
Timer output compare 1 
7.
Timer output compare 2 
8.
Timer output compare 3 
9.
Timer output compare 4 
10.
Timer input capture 4/output compare 5 
11.
Timer overflow 
12.
Pulse accumulator overflow 
13.
Pulse accumulator input edge 
14.
SPI transfer complete 
15.
SCI system (refer to 
Figure 5-7
) 
Any one of these interrupts can be assigned the highest maskable interrupt priority 
by writing the appropriate value to the PSEL bits in the HPRIO register. Otherwise, 
the priority arrangement remains the same. An interrupt that is assigned highest 
priority is still subject to global masking by the I bit in the CCR, or by any associated 
local bits. Interrupt vectors are not affected by priority assignment. To avoid race 
conditions, HPRIO can be written only while I-bit interrupts are inhibited. 
F
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