CAN transmit enable register

[SARY]

hi

  can anyone tell me which flag should be enabled for transmitting data  on CAN in MC9S12XHZ512 controller.

 I want to send some CAN request data from controller after certain time interval.

For this should I set  CAN0TFLG =1 so that  it automatically reaches to interrupt function  or is there any other register  .

let me know if anyone has some idea

rgds

SARY

[kef]

There are 3 CAN TX buffers. There are three corresponding "TX buffer is empty" flags in CANxTFLG register. And there are three "TX buffer is empty"-interrupt enable bits in CANxTIER register.

If you want interrupt on TX buffer 0 is empty, then you do CAN0TIER |= CAN0TIER_TXEIE0_MASK; .

If you want interrupt on any TX buffer is empty, then you set all three TXEIE bits.

You do CAN0TFLG = CAN0TFLG_TXE0_MASK;  to clear buffer 0 flag and send TX buffer 0. TX1 - for TX buffer 1, TX2 - for TX buffer 2.

[SARY]

hi kef

   I got the answer .I can transmit data using this. But there is another problem coming.It always keeps on sending same data even if I have changed data.

Like I want to send two request,I am sending them like

///Fuel cons req. uisng EA00 PGN
   CAN0TFLG|=CAN0TFLG_TXE0_MASK;
  Fuel_cons=(unsigned long)J1939TripFuelCalc;//reading fuel cons data

///Eng hours req. uisng EA00 PGN
   CAN0TFLG|=CAN0TFLG_TXE0_MASK;
  EngHr=J1939HrsCalc;//reading engine hrs

But I am able to receive only first request message.I cant receive second request message.

so what could be the posible reason for that.even I tried to put some  delay between the two request.

but still its not coming.

wating for reply

Thanks

SARY

[kef]

First of all, ORing CANTFLG with something is wrong!

   CAN0TFLG|=CAN0TFLG_TXE0_MASK;

^^ this clears not only TXE0 bit, but also TXE1 and TXE0 if they are set! In other words if TX1 and TX2 buffers are empty, then red line with send those empty buffers.

   CAN0TFLG = CAN0TFLG_TXE0_MASK;

^^ this will send only buffer TX0.

I don't see where are you filling TX buffers. I hope you fill TX buffer only when TXE0 bit is set. Is it so? Because your code looks bit weird: 1) you send TX0 buffer, 2) you do something to Fuel_cons, 3) you send TX0 buffer again, though I don't see where you are waiting for TX0 buffer to become empty (while TXE0 is clear), 4) you do something to EngHr

[SARY]

I have removed Oring also.It is behaving in the same manner.And I am putting data in the transmit buffer  in the CAN transmit interrupt function.Code is somewhat like below

CAN0TBSEL = CAN0TFLG;       // Select lowest empty buffer
    u8TxBuffer = CAN0TBSEL;        // Backup selected buffer

 *((unsigned long*) ((unsigned long)(&CAN0TXIDR0)))= u32ID;         
        // Load data to Data Segment Registers
        for (i=0;i<u8Length;i++) {
            *(&CAN0TXDSR0 + i) = u8TxData[i];  
        }

    CAN0TXDLR = 8;   // Set Data Length Code
    CAN0TXTBPR = 1;    // Set Priority
    CAN0TFLG = u8TxBuffer;  // Start transmission
   
    while ( (CAN0TFLG & u8TxBuffer) != u8TxBuffer);

return;   

But I am able to  receive Only one  data(request frame) in regular intervals.

I want to know how can I transmit two data frames(request) one after the other in regular intervals.

SARY

[VickLiui]

while(!((CAN0TFLG ==0x7)||(CAN0TFLG == 0x6)));
    
    CAN0TBSEL = CAN0TFLG;
        
    CAN0TXIDR3 = (unsigned char)((id & 0x7f)<<1) ;
    CAN0TXIDR2 = (unsigned char)((id>>7) & 0xff) ;
    CAN0TXIDR1 = (unsigned char)(((id>>15) & 0x07) | 0x18 | ((id>>13) & 0xe0));
    CAN0TXIDR0 = (unsigned char)((id >> 21) & 0xff);
 
 
      CAN0TXDSR0 = packet[0];        
      CAN0TXDSR1 = packet[1];
      CAN0TXDSR2 = packet[2];
            
      CAN0TXDSR3 = packet[3];
      CAN0TXDSR4 = packet[4];
      CAN0TXDSR5 = packet[5];
      CAN0TXDSR6 = packet[6];
      CAN0TXDSR7 = packet[7];
      
    CAN0TXDLR = length;
    

    
      CAN0TXTBPR = 0;
 
 
 
 
 
 
      CAN0TFLG = CAN0TBSEL;

[kdn]

Hello I'm also working on MC9S12XHz512 CAN module and getting same problem can someone help me?

[VickLiui]

you can use easily the code

 CAN0TFLG = CAN0TBSEL