G30 Crystal Clock Frequency from 12 MHz to 24 MHz

NETMF & Gadgeteer
1

Hello GHI Forum,

I see in the spec that the G30 MUST run off of a 12 MHz external resonator. If that’s the case then forgive me for questioning a clear statement, but I’m reading it as maybe “g30 must run off of some external resonator.”

So my question then is can I use a faster crystal? 16 MHz, 24 MHz?

The raw chip can handle 26 MHz, how about the netmf?

Thank you

2

@ jwizard93 - there chip doesn’t fun at 12mhz, but it requires a 12mhz Crystal.

No you can’t use any other value. I hope this helps.

3

Just to clarify what Gus said. The chip runs at 84MHz. In simple terms the 12MHz crystal is multiplied up to run at a higher clock rate.

I havent dived into the details of this chip but its normally possibly to adjust the PLL multiplier and divider registers to overclock or underclock the chip (of various parts of it). Ther are likely to be side effects however. I have done a lot of underclocking on the G120 to save power.

I beleive one reason for the 12MHz base clock rate is to run the USB peripheral.

4

Ahh a PLL I should have guessed. I was having a hard time resolving the apparent speed of the device with the fact that I saw a 12 MHz clock on the board. I don’t necessarily see that I have a speed issue, just wanted to make sure I wasn’t missing out on speed I could easily obtain.

Thanks guys!