NPN proximity switch interface to 89c51

IanP said:

The attached picture shows connection between a proximity sensor and 8051 microcontroller without isolation via. Interrupt_0 pin ..

These switches have usually N/O [normally-open] output, that is when nothing is in the proximity of the sensor the output is in high-impedance stage and the voltage is determined by the pull-up [4.7k] resistor ..

On power-on the 8051-derivative has the Interrupt_0 active on the falling edge, so when something triggers the sensor the voltage drops down and the Interrupt_0 will become active ..

In the beginning of your code define a flag as:

Code:

Flags		DATA	20h
Proximity_1	BIT	Flags.0

And then set it in the ISR[Interrupt Service Routine]:

Code:

Int_0:
	SETB		Proximity_1
	RETI

Do we have to write this code in the program as it is?

---------- Post added at 19:41 ---------- Previous post was at 19:31 ----------

And can you pls explain is how it works....

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