68300

Charlie,

After changing the X bit to 1 an the new W and Y values, the system
frequency is ok now.

Many thanks for your help.

Joachim



-----Urspr\ufffdngliche Nachricht-----
Von: "Melear Charles-rdph40" <charles.melear@...>
An: <68300@yahoogroups.com>
Gesendet: Montag, 16. Dezember 2002 15:50
Betreff: RE: [68300] 68332 clock frequency


> Joachim,
>
> There are two problems that you need to be aware of.
>
> 1.  The only mask set of the MC68332 that is in production is J30C.  (J66A
is an identical mask set made in another wafer line.)  For J30C and J66A,
the 3-component XFC filter is required.  If you don't use the 3-component
filter, your circuit will have clock jitter.  Sometimes it can get bad
enough to mess up asynchronous serial communications devices and cause bit
error problems.
>
> 2.  If you DO NOT set the X bit = 1 in the SYNCR register, the VCO will
run too fast, lose lock and then all bets are off on what system frequency
will result.  So, if you are going to run the system clock above 8.3 MHz,
the X bit in the SYNCR register MUST (there are no other options here) be
set to a logic 1.  Then, calculate the W and Y bits to get the frequency you
want.
>
> Let me know if this works.
>
> Charlie
>
> -----Original Message-----
> From: Entwicklung [mailto:Entwicklung@...]
> Sent: Monday, December 16, 2002 8:40 AM
> To: 68300@yahoogroups.com
> Subject: [68300] 68332 clock frequency
>
>
> Hello everyone.
>
> I have two questions to the clock generator of the MC68332CFC25MHz
> with a 32,768 kHz reference.
> Does somebody know the maximum of the clock freqency I can reach.
> In my system the clock frequency is ok till 20,971Mhz. Higher values in
the
> sync-register, which forces greater frequencies than 20,971MHz are not
> stable.
> And the frequencies are not equal to the value I expected.
>
> Is this normal effect, or could be something wrong with my device.
>
> Thanks
> Joachim
>
>
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