MPC5777C new silicon, M_CAN_0 CAN_FD and Clock Frequency

[markus_fischer1]

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.

#if XXX_MCAN_L_BRS_DEF

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;

　

#else

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;

#endif

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.

SIU.SYSDIV.B.MCANSEL = 0;

SIU.HLT2.B.MCANA = 0;

SIU.HLT2.B.MCANB = 0;

[PetrS · Accepted solution]

Hi Marcus,

the example posted on the community was created and tested on previous MCU cut (2N45H).
There are several changes in registers between versions, so if you have latest one, you should follow latest RM for a proper registers definition. A MPC5777CRMAD (https://www.nxp.com/docs/en/reference-manual/MPC5777CRMAD.pdf) have to be used when using 2N45H mask.

for a CCCR register

3N45H

2N45H

so the code on latest revision could be as below

// put module to Init mode    

MCAN_0.CCCR.B.INIT = 0x1;    

while(MCAN_0.CCCR.B.INIT == 0)    {     asm("nop");     }    

// enable CCE bit to change config    

MCAN_0.CCCR.B.CCE = 0x1;    

while(MCAN_0.CCCR.B.CCE==0)     {     asm("nop");     }

#if BRS    

   MCAN_0.CCCR.B.FDOE = 0x1;    // enable CAN FD    

   MCAN_0.CCCR.B.BRSE = 0x1;    // enable bit rate switching    

   ....

#else    

   MCAN_0.CCCR.B.FDOE = 0x1;    // enable CAN FD    

   MCAN_0.CCCR.B.BRSE = 0x0;    // disable bit rate switching    

   ....

#endif

For a CAN bit timing again there is significant difference in registers. On 3N45H registers are named NBTP and DBTP (TDCR if TDC is also enabled) while on 2N45H it was BTP and FBTP. So you must set it properly to have correct timing.

BR, Petr