CAN sample point selection in zvml64 mcu

[pratayay123]

Hi,

I am using S12ZVML64 MCU.

For Can Baudrate of 500Kbps

i am checking on two different bus clock

1) With bus clock of 25MHz as CAN source clock 

Time Segment 1 = 16Tq

Time segment 2 = 8Tq

Prescaler value = 2

SYNC_SEG = 1

Sampling Point(%) as calculated is 68%

2) With bus clock of 20MHz as CAN source clock 

Time Segment 1 = 12Tq

Time segment 2 = 7Tq

Prescaler value = 2

SYNC_SEG = 1

Sampling Point(%) as calculated is 65%

So I want to ask what are the parameter on which sample point (%) selection is decided and is it possible to achieve the same sample point percentage for different frequency i.e 20Mhz and 25Mhz

what is the deciding factor for selection of sampling point for the s12zvml64 MCU.

[lama]

Hi,

sampling point is up to the user or some specification.

A good general rule is to set the sample point above 80%. Based on the experiences of the automotive industry, the selected sample point should be near the 80% value.

To play a small game you can use https://community.nxp.com/t5/S12-MagniV-Microcontrollers/CAN-setup-calculator-for-S12-X-and-MagniV-d...

where all combinations are calculated and suitable ones are highlighted.

https://www.nxp.com/docs/en/application-note/AN1798.pdf

Best regards,

Ladislav