Hi,
I am going to use FTM capture mode for period measurement. Looking into the datasheet (VYBRIDRM.pdf), possible FTM clocks are: system clock, fixed frequency clock, external clock. I have not found a direct description of what the "system clock" is for FTM. I assumed that it is the System Core Clock for A5, that is, around 396MHz or so. But sample code showed that the real clock is only 66MHz (while A5 clocked at 396MHz). PDF references for other CPUs with FlexTimer explicitly tell that "FTM system closk is the bus clock, around 66MHz", but VYBRIDRM.pdf does not explain this (or I missed that). At the same time the table 9-10 (page 628) introduces "flex_root_clk" clock name, for which the maximum frequency is 85MHz. This flex_root_clk is found in the document just once, and no more references to it. It looks like FTM clock = Bus clock.
So my questions are:
Thanks!
Solved! Go to Solution.
Hi,
The clocking of FTM is shown below:
FTM has options for Fixed clock, System clock, and External clock. The system clock is fixed at IPG_Clk divided by 2, so is 83 MHz is the IPG clock (or CM4 ) is running at 167MHz. All other clocks have to follow the relation as stated in the Reference Manual. I am quoting them again below:
As far as the IO speed is concerned, I don't think the IO's will have a problem propagating a 42MHz signal (half of 83 MHz).
Best Regards,
Alejandro
> The system clock is fixed at IPG_Clk divided by 2, so is 83 MHz is the IPG clock (or CM4 ) is running at 167MHz
Shoudn't this be IPG clock = Platform Bus or CM4 Clock / 2? (Table 6-6 Clocking Configuration).
And then the undefined 'system clock' in the manual is actually = IPG clock, not IPG / 2.
Thank you for the answer.
It seems to be correct, but FTM clocking diagram does NOT show "system clock". So could you please point me to the statement in a document where "The system clock is fixed at IPG_Clk divided by 2" is written? I did not find it so asked the question. Or, if it is not documented, then would be good to have it finally fixed in the manual. Still, I believe that I missed that.