How to achieve baud rate of 500kbps with the bus clock frequecy of 25.6 MHz for MSCAN

[krishnakarthik]

I am using the MM9Z1_638 micro controller for batter management.

I am not able to achieve 500 Kbps baud rate when i am using the bus clock as the input to the MSCAN and my bus clock is set to frequency of 25.6 Mhz

[RadekS]

Hi krishna,

I am afraid that you cannot set exact 500kbps CAN bus clock with 25.6MHz bus clock source.

I would like to highly recommend use external oscillator instead of PLL for real CAN nodes. PLL as clock source is fine for debugging, however we cannot be sure with clock accuracy due to PLL unlock range up to 2.5%. 8 or 16MHz crystal should be fine; 4MHz is probably too slow for 500kbps.

Optionally you could trim IRC oscillator to 1MHz instead of 1.024MHz. However I am afraid that this do not brings equivalent benefit in compare to amount of work for trimming.

In attachment you could look at CAN baudrate calculator.

I hope it helps you.

Have a great day,
RadekS

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[krishnakarthik]

Hi Radek,

Thanks for info

[kef2]

Not likely to be possible.

Is it possible to switch MSCAN clock source on MM9Z1 to oscillator clock? Perhaps it is more suitable?