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MPC5777C new silicon, M_CAN_0 CAN_FD and Clock Frequency

Question asked by Markus Fischer on Oct 22, 2018
Latest reply on Oct 26, 2018 by Petr Stancik

Good Morning,


I have 2 issues with programming the MPC5777C.

First One:

-> I want tu use the CAN_FD Option from M_CAN_0 (ISO CAN Works already)

so i Change the Parameter for can FD with and withouth Bitrate switching from example.



In my Init i wait for CCCR.INIT and CCCR.CCE for Setting 0.


After this Operation, i make the cmr request and set the can Mode with cme. The CCCR.CME bit is set in Expression view. On the other side the CCCE.FDBS and CCCR.FDO bits for the request are set no time.



M_CAN_0.CCCR.B.CMR = 0x2; // enable CAN FD with bit rate switching

M_CAN_0.CCCR.B.CME = 0x2;


M_CAN_0.BTP.B.BRP = 1u; //4

M_CAN_0.BTP.B.SJW = 3u;

M_CAN_0.BTP.B.TSEG1 = 4u; //12

M_CAN_0.BTP.B.TSEG2 = 2u; //0


M_CAN_0.FBTP.B.FBRP = 0x0u;


M_CAN_0.FBTP.B.FSJW = 0x3u;

M_CAN_0.FBTP.B.FTSEG1 = 0x4u;

M_CAN_0.FBTP.B.FTSEG2 = 0x2u;



M_CAN_0.CCCR.B.CMR = 0x1; // enable CAN FD without bit rate switching

M_CAN_0.CCCR.B.CME = 0x1;


M_CAN_0.BTP.R = 0x00011E77; // Set time quanta for 0.5Mbps

M_CAN_0.BTP.B.SJW = 5;

M_CAN_0.BTP.B.TSEG1 = 16;

M_CAN_0.BTP.B.TSEG2 = 1;





My Second issue is, that the MCAN clock is wrong. If i calculate the frequency back from my Settings, i recieve a frequency from 8.1 MHz. But i have choose xosc as clock source and Programm the extal pin in the dcf(XOSCEN=0) record as xosc. There is a 40MHz oscillator connected to this pin. So i don´t know why the freuency is so low.