AT89C51IC2-SLSCM datasheet(58/146 Pages) ATMEL

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AT89C51IC2

4301A–8051–01/04

Interrupt System

The AT89C51IC2 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,

Two Wire Interface (I2C) interrupt, Keyboard interrupt and the PCA global interrupt.

These interrupts are shown in Figure 22.

Figure 22. Interrupt Control System

Each of the interrupt sources can be individually enabled or disabled by setting or clear-

ing a bit in the Interrupt Enable register (Table 51 and Table 49). 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 52) and in the

Interrupt Priority High register (Table 50 and Table 51) shows the bit values and priority

levels associated with each combination.

IE1

High priority

interrupt

Interrupt

polling

sequence, decreasing from

high to low priority

Low priority

interrupt

Global Disable

Individual Enable

EXF2

TF2

TF0

INT0

INT1

TF1

IPH, IPL

IE0

PCA IT

KBD IT

SPI IT

TWI IT

AT89C51IC2-SLSCM Datasheet(PDF) 58 Page - ATMEL Corporation