AT89C51ID2_14 Datasheet, PDF (63/157 Pages) ATMEL Corporation – Six 8-bit I/O Ports (64 pins or 68 Pins Versions)

AT89C51ID2
Interrupt System
The AT89C51ID2 has a total of 10 interrupt vectors: two external interrupts (INT0 and
INT1), three timer interrupts (timers 0, 1 and 2), the serial port interrupt, SPI interrupt,
Keyboard interrupt and the PCA global interrupt. These interrupts are shown in Figure
25.
Figure 25. Interrupt Control System
INT0
IE0
TF0
INT1
IE1
TF1
PCA IT
RI
TI
IPH, IPL
3
0
3
0
3
0
3
0
3
0
3
0
High priority
interrupt
Interrupt
polling
sequence, decreasing from
high to low priority
TF2
EXF2
KBD IT
TWI IT
SPI IT
3
0
3
0
3
0
3
0
Individual Enable
Global Disable
Low priority
interrupt
Each of the interrupt sources can be individually enabled or disabled by setting or clear-
ing a bit in the Interrupt Enable register (Table 52 and Table 50). This register also
contains a global disable bit, which must be cleared to disable all interrupts at once.
Each interrupt source can also be individually programmed to one out of four priority lev-
els by setting or clearing a bit in the Interrupt Priority register (Table 53) and in the
Interrupt Priority High register (Table 51 and Table 52) shows the bit values and priority
levels associated with each combination.
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