Table 13-1. Interrupt Enable (IE) Register
(MSB)
(LSB)
EA
–
ET2
ES
ET1
EX1
ET0
EX0
Enable Bit = 1 enables the interrupt.
Enable Bit = 0 disables the interrupt.
Symbol
Position
Function
Disables all interrupts. If EA = 0, no interrupt is acknowledged. If EA = 1, each
interrupt source is individually enabled or disabled by setting or clearing its enable bit.
EA
IE.7
–
IE.6
IE.5
IE.4
IE.3
IE.2
IE.1
IE.0
Reserved.
ET2
ES
Timer 2 interrupt enable bit.
Serial Port interrupt enable bit.
Timer 1 interrupt enable bit.
External interrupt 1 enable bit.
Timer 0 interrupt enable bit.
External interrupt 0 enable bit.
ET1
EX1
ET0
EX0
User software should never write 1s to reserved bits, because they may be used in future AT89 products.
Figure 13-1. Interrupt Sources
0
INT0
IE0
1
TF0
0
1
INT1
IE1
TF1
TI
RI
TF2
EXF2
18
AT89S52
1919C–MICRO–3/05
ATMEL [ ATMEL ]
