OLED1 XPlained Pro ATSAMC21N Xplained Pro SERCOM Clocking setup confustion

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I have an example "Hello world" working with ATSAMC21N Xplained Pro board and the OLED1 Xplained Pro board

the 48 MHz internal oscillator is divided down to 4MHz and passed to the CPU and SPI_INSTANCE (both Core & Slow clocks) via clock generator 0 with a clock divisor of 1.

 

If I change OSC48M to a division selection of 0x0 (instead of the 0xb that divides it down to 4 Mhz) and then change the divisor of clock generator 0 to 12 so the CPU and SERCOMM  are all both clocked at 4Mhz the SERCOM stop transmitting anything and the display no longer updates (Note the OLED1 Xplained Pro is connected to the EXT3 Header so its using SERCOM7)

 

I don't understand why this would not work?

 

Ideally what I need to do is clock the CPU at 48MHz and clock the SERCOM at 4Mhz so I can do fast computations on other algorithms but still update the OLED display.  I get behavior similar to case 2 above with the OSC48M not divided down if I attempt to passe the 48MHz to CPU via clock generator 0 with a divide by 1 and a 4 Mhz to the SERCOM via clock generator 1 divided down by 12 to 4Mhz.

 

What am I missing about using the internal oscillator at 48MHz?

 

 

Thanks

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Configure 2 wait states for NVM (with Atmel Start this is in MCLK).

BTW, you are posting in the wrong place, this is for AVR.

/Lars