
110
7663E–8051–10/08
AT89C51RE2
Registers
Table 80. Priority Level Bit Values
A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-prior-
ity interrupt. A high-priority interrupt can’t be interrupted by any other interrupt source.
If two interrupt requests of different priority levels are received simultaneously, the request of
higher priority level is serviced. If interrupt requests of the same priority level are received simul-
taneously, 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.
iph. x
ipl. x
interrupt level priority
0
0 (lowest)
011
102
1
3 (highest)