10

AT89LS51

3053A–8051–05/02

.

Figure 1. Interrupt Sources

Table 4. Interrupt Enable (IE) Register

(MSB)

(LSB)

EA

–

–

ES

ET1

EX1

ET0

EX0

Enable Bit = 1 enables the interrupt.

Enable Bit = 0 disables the interrupt.

Symbol

Position

Function

EA

IE.7

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.

–

IE.6

Reserved

–

IE.5

Reserved

ES

IE.4

Serial Port interrupt enable bit

ET1

IE.3

Timer 1 interrupt enable bit

EX1

IE.2

External interrupt 1 enable bit

ET0

IE.1

Timer 0 interrupt enable bit

EX0

IE.0

External interrupt 0 enable bit

User software should never write 1s to reserved bits, because they may be used in future AT89

products.

IE1

IE0

1

1

0

0

TF1

TF0

INT1

INT0

TI

RI