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How should I connect the RESET pin in a microcontroller (AT8051), and why in that particular way?

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A fast search on Google gave me this:

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The first circuit pulls the RESET pin low to enable the chip. The second circuit is the same, but with a reset button. If you press that, the chip will get reset.

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Maybe add a normally reverse biased diode across the resistor; when power is shut-off the 5V collapses to 0V and there is a possibility the reset pin will see negative voltages due to charge on capacitor. – Andy aka May 1 at 7:18
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What about the ESD protection diodes that are almost surely already in the package? – Phil Frost May 1 at 11:00
How does the RESET work? Why to give a RESET pin & how does it auto RESET in fig.(1) ? What's the concept? RESET pin is reset just by giving a +5V. Then why that kind of circuit? Simple connect +5V to push btn switch & then to RESET pin. That's it. Isn't it? – abhisekp May 3 at 15:17
Why the caps are used? And why the pull up & pull down? – abhisekp May 3 at 15:19
@abhisekp when RESET is high, the device goes into "RESET mode", it doesn't do a thing until it gets out of this mode. So you'll have to get the device out of RESET, so you need to pull the pin down (with the resistor). Otherwise, the pin floats and you can't rely on the device getting out of RESET. The cap is added to make sure the device isn't reset due to EMI. – Camil Staps May 3 at 15:20
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