CPU Reset Circuit with oscillator stop

[bhavanireddy]

CPU Reset Circuit

I came across this reset circuit while going through a reference design. What exactly he is doing to reset the microcontroller through XTAL_IN and XTAL_OUT pins through transistors? Any advantages of using this design?

 

[kender]

CPU Reset Circuit

Just guessing. The actual CPU reset is done with the RESET<< output (which is connected elsewhere). Notice that RESET<< is active-high. The purpose of Q2 is to stop the XTAL from oscillating while CPU is in reset. Q2 ties one side of XTAL to ground. Q1 only matches Q2 to provide symmetrical loading for the XTAL when it's oscillating.

 

[bhavanireddy]

Re: CPU Reset Circuit

Thanks Kender. The RESET signal in the attached schematic only resets LCD and JTAG. It is not connected to CPU. In fact, the CPU I.MX23 doesn't have a reset pin. I was just wondering how to reset the micro controller without the reset pin.

-B