i.MX7D: flextimer on M4 bare metal firmware

Dear All,

I’m designing the schematic of a board and I need to know in advance which would be the limits to the flextimer frequency.
In particular, I need to know which clock is used to feed the FTM counters, given that the FTM will be used by a baremetal firmware running on the M4.

From the reference manual of the i.MX7D I read that the FTM has a single clock selection option, system clock: well, which clock is the ‘system clock’ when used within the M4?

Thanks and regards,

Since the peripherals are on a shared bus they are clocked independently from the CPU. So system clock likely refers to a common bus clock and is independent from whether it is accessed from the M4 or A7.

I assume that the system clock refers to the main FlexTimer clock, which can be configured in the CCM (Clock Controller Module). One can select between different clock sources for FLEXTIMER1_CLK_ROOT. I think the default is 0, which is the external 24MHz clock. You can change the root clock by using CCM_UpdateRoot, e.g.

CCM_UpdateRoot(CCM, ccmRootFtm1, ccmRootmuxFtmOsc24m, 0, 0);

The reference manual states an upper limit of 67.5MHz.

Thank you for your prompt reply!