at89c51re2-slsem ATMEL Corporation, at89c51re2-slsem Datasheet - Page 110

• Manufacturer Part Number: at89c51re2-slsem
• Description: At89c51re2 8-bit Flash Microcontroller
• Manufacturer: ATMEL Corporation

Interrupt System
Figure 28. Interrupt Control System
7663B–8051–03/07
RI_1
TI_1
SPI IT
EXF2
KBD IT
INT0
INT1
PCA IT
TF0
TF1
TF2
RI
TI
Individual Enable
The AT89C51RE2 has a total of 10 interrupt vectors: two external interrupts (INT0 and
INT1), three timer interrupts (timers 0, 1 and 2), two serial ports interrupts, SPI interrupt,
Keyboard interrupt and the PCA global interrupt. These interrupts are shown in Figure
28.
Each of the interrupt sources can be individually enabled or disabled by setting or clear-
ing a bit in the Interrupt Enable register (Table 78 and Table 76). 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 79) and in the
Interrupt Priority High register (Table 77 and Table 78) shows the bit values and priority
levels associated with each combination.
IE0
IE1
IPH, IPL
Global Disable
3
0
3
0
3
0
3
0
3
0
3
0
3
0
3
0
3
0
3
0
High priority
interrupt
Interrupt
polling
sequence, decreasing from
high to low priority
Low priority
interrupt
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