CPU frequency issue

Embedded Devices NET+OS
#1

Hi,

I wonder if on the CC9C module there’s a way for controling the CPU frequency. For example by setting some GPIOs for some time at startup.

There is nothing of such on the datasheet of the module, but I am experiencing a frequency fall on a board that I have developped (following the design guides and the schematics of the DiGi eval board).
When I put the module on the DiGi board, it runs at ~150MHz (the frequency on the datasheet). When I put it on my board it runs at 50MHz !
I tried to compare the SoDIMM signals, everything is identical.
What could be the reason for such frequency difference.
I do not use the USB part of the module so I do not provide the 5V to the module. Can this be the reason?
On my board, the only signals that are used are the 4 serial ports signals.

Regards,
Alain

#2

It is hard to say if the following could cause this condition, but I would carefully check the GPIO pins.

When using the CC9C you’ll want to pay attention to when the UBUFFEN (pin 8) goes low, as this means the GPIO pins are ready to be used. Creating any kind of load or driving the pins during boot up (before the UBUFFEN goes low) can cause the NS9360 to get into an unknown state.

For further reference, check the CC9C Hardware Reference Manual, page 70.

http://ftp1.digi.com/support/documentation/90000789_C.pdf