RT1062 CAN clock shared by controllers?

jim_verheijde — Wed, 16 Sep 2020 15:06:47 GMT

Hi all,

I working with the RT1062 chip. I am trying to use the CAN controllers for communication. I want to use both the CAN2 at 1Mbit/s and CAN_FD controller (CAN3) at 8Mbit/s. To do this I must use a CAN_CLK of 80Mhz so I choose the following values which selects the pll3 (480Mhz) and divides by 6 and then by 1 to get 480Mhz/6/1=80Mhz:

#define FLEXCAN_CLOCK_SOURCE_SELECT (2U) #define FLEXCAN_CLOCK_SOURCE_DIVIDER (0U) CLOCK_SetMux(kCLOCK_CanMux, FLEXCAN_CLOCK_SOURCE_SELECT); CLOCK_SetDiv(kCLOCK_CanDiv, FLEXCAN_CLOCK_SOURCE_DIVIDER);

For the CAN_FD controller this works fine, however, when using these clock settings with the CAN2 controller it doesn't work and I get the following errors when connecting via a CAN-USB connector.

However when using lower clock speeds by dividing by 4 for example to get 480Mhz/6/4=20Mhz:

#define FLEXCAN_CLOCK_SOURCE_SELECT (2U) #define FLEXCAN_CLOCK_SOURCE_DIVIDER (3U) CLOCK_SetMux(kCLOCK_CanMux, FLEXCAN_CLOCK_SOURCE_SELECT); CLOCK_SetDiv(kCLOCK_CanDiv, FLEXCAN_CLOCK_SOURCE_DIVIDER);

CAN2 works again, however CAN_FD can only run at 2Mbit/s.

So my questions are:

Can I use different clocks for the different clock controllers, or are they always shared?
Or alternatively, how can I make the CAN2 controller work with a CAN_CLK of 80Mhz at 1Mbit/s?

Re: RT1062 CAN clock shared by controllers?

jeremyzhou — Thu, 17 Sep 2020 06:04:09 GMT

Hi,

Thank you for your interest in NXP Semiconductor products and for the opportunity to serve you.
1）Can I use different clocks for the different clock controllers, or are they always shared?
-- No, I'm afraid not, they've shared the same root clock.

Have a great day,
TIC

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