Kirk Humphries

3.3 v operation

Discussion created by Kirk Humphries Employee on Jan 26, 2006

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Posted: Sun Dec 18, 2005  8:13 pm

 

I can't seem to tget my XDP512 to run at less than around 4.5 v. Shouldn't it run at 3.3?

 


 

Posted: Mon Dec 19, 2005  1:22 am

 

Yes, the MC9S12XDP512 can run at either 5V or 3.3V. I have verified this personally on our emulator.

 

Hope this helps,

 


 

Posted: Mon Dec 19, 2005  2:54 am

 

> Yes, the MC9S12XDP512 can run at either 5V or 3.3V. I have verified this personally

> on our emulator.

 

The only thing to watch for is that at 3.3V you can only run at 16MHz if you use the external bus. If you use internal only (i.e. single-chip mode), then you can run at 25MHz. The manuals are a bit hazy about that but we asked Freescale and that was the official answer.

 


 

Posted: Mon Dec 19, 2005  4:05 am

 

Your answer is correct for the HCS12 parts, but the question was on an S12X part.

 

On S12X the bus rates are higher - the internal bus is specified for 40MHz bus-speed, and the external bus for up to 40MHz bus speed in emulation modes, or 20MHz bus speed in normal expanded mode (when operated with the minimum 1 wait-state in Normal Expanded mode).

 

At room temperature my tests show the S12X external bus runs well even higher than the specification - at 50MHz bus speed at either 5V or 3.3V in emulation modes.

 

It is true that the external drivers are weaker at 3.3V, but given a proper design, in my experience it is possible to operate at the maximum bus speed at both 3.3V and 5V.

 

Hope this helps,

 


 

Posted: Mon Dec 19, 2005  10:22 am

 

> I can't seem to tget my XDP512 to run at less than around 4.5 v.

> Shouldn't it run at 3.3?

>

 

 

Just a guess…

 

Might it be because your board is stuffed with an external LVI?

 


 

Posted: Tue Dec 20, 2005  3:23 pm

 

> > I can't seem to tget my XDP512 to run at less than around 4.5 v.

> > Shouldn't it run at 3.3?

> >

>

 

> Just a guess...

>

 

> Might it be because your board is stuffed with an external LVI?

 

I'm such a moron. That's what it was.

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