Datasheet

31
3286P–MICRO–3/10
AT89S8253
Interrupt Source Vector Address
System Reset RST or POR 0000H
External Interrupt 0 IE0 0003H
Timer 0 Overflow TF0 000BH
External Interrupt 1 IE1 0013H
Timer 1 Overflow TF1 001BH
Serial Port RI or TI or SPIF 0023H
Table 15-1. Interrupt Enable (IE) Register
IE Address = A8H Reset Value = 0X00 0000B
Bit Addressable
EA – ET2 ES ET1 EX1 ET0 EX0
Enable Bit = 1 enables the interrupt, 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.
ET2 IE.5 Timer 2 interrupt enable bit.
ES IE.4 SPI and UART 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.
Table 15-2. IP – Interrupt Priority Register
IP = B8H Reset Value = XX00 0000B
Bit Addressable
– – PT2 PS PT1 PX1 PT0 PX0
Bit76543210
Symbol Function
PT2 Timer 2 Interrupt Priority Low
PS Serial Port Interrupt Priority Low
PT1 Timer 1 Interrupt Priority Low
PX1 External Interrupt 1 Priority Low
PT0 Timer 0 Interrupt Priority Low
PX0 External Interrupt 0 Priority Low