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Clocking questions + ccm

Question asked by webjorn.gullik on Nov 11, 2013
Latest reply on Nov 12, 2013 by webjorn.gullik
I have just ported one of my systems over to the STM32F4Discovery board. It is a small OS + TCP/IP. However, I stumbled on a few things:
I need to have a 8 khz interrupt for audio sampling. I think I have clocks OK, 8 Mhz HSE, PLLM=8, N=336, P=2, Q=7, but I have to assume TIM2 clock is 84 Mhz, to get down to 8 khz, pre=420, period=25. Do I actually have the bus at 84 Mhz, 42 is maximum allowed? Or is the peripheral clock different from BUSclock?

2. Why does the ld examples never use the 64 kbyte CCM? I guess it could be used as heap + stack at an advantage, but everybody seems to skip this area. Also is it slower / faster than "ordinary" ram?