why pullup resistor and why the capacitors in the mC oscillator ciruit ?

Thread Starter

Embedded Lover

Joined Dec 22, 2008
26
Hi All ,

I have 2 questions here ,

I am using 8051 mC and when using porto , it says I have to connect it to pullup resistor . I know pullup resistor is not for mC work only it has a general function I want to know it well .

Second question ,



For clock generation a crsytal oscillator is used as picture above.when connecting the crystal oscillator , they also connect 2* 30pF capacitors I want to know their function , why they are here ?

also the reset pin has the capacitor and resistance. why they are here and what determines their values ?.


Thanks in advance .
 

SgtWookie

Joined Jul 17, 2007
22,230
The resistor and capacitor on the RESET line exist so that when power is first applied, the RESET line is pulled high until the 8.2k resistor drains enough charge from the capacitor until the RESET line falls to a logical low level. This helps to ensure that the mC starts up in a known state.
 
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