also set the Bit rate of 52235evb'CAN?

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case 1000000:

CANCTRL = ((3 << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME2 | PHASE_BUF_SEG1_LEN3 | PHASE_BUF_SEG2_LEN2);

PRESDIV=3;
RJW_2=2,
EXTAL_CLK_SOURCE =0;
PROPSEG_BIT_TIME2   (1)       =1;
PHASE_BUF_SEG1_LEN3 (2<<19)           =2;
 PHASE_BUF_SEG2_LEN2 (1<<16)   =1;
because the EXTAL_CLK=25000000;
so  Ftq = 25000000/(3+1);
Sync_Seg + Prop_Seg +Phase_Seg1 + Phase_Seg2=1+(1+1)+(2+1)+(1+1)=8
BIT RATE= Ftq /(1+1+1+2+1+1+1)!=1000000;?ERROR??

BUT THE
default:                                                             // 40 KHz
        CANCTRL = ((24 << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME8 | PHASE_BUF_SEG1_LEN8 | PHASE_BUF_SEG2_LEN8); // Initialise the CAN controller with the required speed and parameters// Initialise the CAN controller with the required speed and parameters
PRESDIV=24;
so  Ftq = 25000000/(24+1);
Sync_Seg + Prop_Seg +Phase_Seg1 + Phase_Seg2=1+(7+1)+(7+1)+(7+1)=25
BIT RATE= Ftq /(25)=40000=40kHZ!

WHY????make sure????which is RIGHT??






       

[mark]

Hi

I have checked and you are right - the speed is proabably about 781kHz instead of 1MHz.

After some pondering I think that I can explain the error. Origianally the CAN interface was developed with the 5213 and an 8MHz crystal - the crystal is used rather than the PLL since it has less jitter and is thus more accurate. The implementation was successfully tested in a system using different CAN controllers at 1MHz - and the speed is exact when the define for this processor is set.

The M5223X has a 25MHz crystal and the setting is not correct for this (if using only M5223X in a system this error will not necessarily be noticed since all are working with the same speed). I suggest the following change which seems to be the only method of generating the exact 1MHz speed from the 25MHz crystal:

        CANCTRL = (((1-1) << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME8 | PHASE_BUF_SEG1_LEN8 | PHASE_BUF_SEG2_LEN8); // Initialise the CAN controller with the required speed and parameters

For 100kHz simply divide the clock by 10:

        CANCTRL = (((10-1) << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME8 | PHASE_BUF_SEG1_LEN8 | PHASE_BUF_SEG2_LEN8); // Initialise the CAN controller with the required speed and parameters

Regards

Mark

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     Thanks you!
     I do that a day!I can sure that now!