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Setting up a 18 MHz timer

Question asked by jdcowpland on Sep 5, 2013
Latest reply on Sep 6, 2013 by jdcowpland
Hi guys,

I've got a stm32f10zg eval board and am trying to set up a timer on it to generate an interrupt at a frequency of 8MHz. I've got the PLL set up a a x9 so that the timer is getting a 72 MHz input clock. I've got my prescaler set to 1, and the arr register set to 8, but the frequency I get out seems to have a maximum of ~800KHz no matter what I try. If i increase the prescaler to 10, I get out an expected 800KHz, and a prescaler of 100 gives me an expected 80KHz and so on. Just can't seem to get past that 800KHz though. Any ideas why? Is it possible that the interrupt is just slowing things down too much?

Ideally I want to be able to set off a DMA transfer at a 8MHz frequency, but just concentrating on the timer just now. If it is the interrupt causing too much lag, is there any way to trigger a DMA transfer from a timer without using an interrupt?