Interrupts
7-31
Program Flow Control
7.6.3
Interrupt Prioritization
When two interrupts occur in the same clock cycle or when two previously
received interrupts are waiting to be serviced, one interrupt is serviced before
the other. The CPU handles this prioritization by servicing the interrupt with the
least priority. The priority of interrupts is handled by the CPU according to the
interrupt vector table. Priority is set according to position in the table—those with
displacements closest to the base address of the table are higher in priority.
Table 7–7 shows the priorities assigned to the reset and interrupt vectors.
Table 7–7. Reset and Interrupt Vector Priorities
Reset or
Interrupt
Vector
Location
Priority
Function
RESET
0h
0
External reset signal input on the RESET pin
INT0
1h
1
External interrupt on the INT0 pin
INT1
2h
2
External interrupt on the INT1 pin
INT2
3h
3
External interrupt on the INT2 pin
INT3
4h
4
External interrupt on the INT3 pin
XINT0
5h
5
Internal interrupt generated when serial-port 0 transmit buffer is empty
RINT0
6h
6
Internal interrupt generated when serial-port 0 receive buffer is full
XINT1
†
7h
7
Internal interrupt generated when serial-port 1 transmit buffer is empty
RINT1
†
8h
8
Internal interrupt generated when serial-port 1 receive buffer is full
TINT0
9h
9
Internal interrupt generated by timer0
TINT1
0Ah
10
Internal interrupt generated by timer1
DINT/
DINT0
0Bh
11
Internal interrupt generated by DMA channel 0
DINT1
‡
0Ch
12
Internal interrupt generated by DMA channel 1
† Reserved on ’C31 and ’C32
‡ Present on ’C32 only