What is an interrupt?

An interrupt is an asynchronous signal that needs attention. An interrupt stops the CPU of a microcontroller, leaving the tasks that it is currently doing, to give attention to the interrupt signal. Once the attention has been given to the interrupt signal, the CPU goes back to its unaccomplished task before the interrupt has occured and continues the task.

The Interrupts of AT89C2051

The interrupts of AT89C2051 is compatible with the interrupts of the original 8051 microcontroller. It has 6 interrupts sources ( 5 interrupts + RESET). The interrupt sources of AT89C2051 are the following:

	Interrupt	Source	Priority Number
1	RESET	RST	N/A
2	External Interrupt 0	IE0	0
3	Timer 0 Interrupt	TF0	1
4	External Interrupt 1	IE1	2
5	Timer 1 Interrupt	TF1	3
6	UART Interrupt	RI or TI	4

Please note that in this tutorial, we will not consider the interrupt from RESET.

The table above shows the interrupt sources of AT89C2051 and their respective interrupt priority number. Knowing the priority number is important specially if two different interrupt sources occur at the same time. [Read more...]

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