GMVS

Question about crystals ( hardware)

Discussion created by GMVS on Apr 11, 2012
Latest reply on Apr 11, 2012 by bigmac

Hi

 

I'm trying to use a MC9S08DZ128MLL

but i still dont undestand the clock part

let's make this a hardware approach

 

the internal reference clock can only provide 25 kHz to 41.66 kHz


1) but i need a real time clock here, so  i need a 32kHz crystal attached... to both XTAL and EXTAL, right?

but what if i want a faster clock sometime?

 

2)lets say i'd want to work at 16MHz someday using the same hardware. is there a way to have both the 32kHz and the 16MHz crystals available to select? or would i have to remove one and place the other manually?

 

 

now, this is a software question

 

3) how do i make the micro work at 40MHz?

in hardware i understand i need to attach a square wave input clock en EXTAL, leaving XTAL free

what would be a good choice for the clk?

and how should i configure the micro to work with this?

 

 thanks 

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