Re: [microblaze-uclinux] Microblaze highest frequency.

[Andreas Hofmann <ahofmann@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Nicolas Herve wrote:

Hi,

> I mean the system clock (indeed the "Processor-Bus clock frequency")
> still is at 100MHz, and have selected the 400 MHz for the CPU only in
> the bsbwizard (at least, I though it wat, indeed it is named
> "Reference Clock Frequency"). Compilation success with the Xplorer
> Scripts option [1] without any complaint.
> Then I presume that the CPU is configured for 400 MHz clock frequency.

No. The "Reference Clock Frequency" is the frequency of your external
clock source. Unless you install a different oscillator in one of the
crystal oscillator sockets on the ML402 board your external clock won't
change.
What you have done is to tell the system that your external clock runs
at 400 MHz. So the clock generator gets configured to divide the input
clock by 4 to create the "Processor-Bus clock frequency". Your system
should now run at 25 Mhz effectively. That's the reason why you're not
seeing any error messages.

The 25 Mhz bus clock will break at least the UART configuration i.e. you
are getting a different, lower baud rate. The same holds for ethernet.

Regards,
Andreas

-- 
Dipl.-Informatiker Andreas Hofmann

Goethe-Universität Frankfurt am Main

Fachbereich Informatik und Mathematik
Institut für Informatik
Studienkoordination

Robert-Mayer-Straße 11-15
D-60325 Frankfurt am Main

Tel.: +49 69 798-28242
Fax : +49 69 798-22351
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