topic Re: CAN transmit enable register in S12 / MagniV Microcontrollers

CAN transmit enable register

SARY — Wed, 12 May 2010 15:59:58 GMT

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

Re: CAN transmit enable register

kef — Wed, 12 May 2010 16:27:58 GMT

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.

Re: CAN transmit enable register

SARY — Thu, 13 May 2010 14:16:52 GMT

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

Re: CAN transmit enable register

kef — Thu, 13 May 2010 14:56:39 GMT

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

Re: CAN transmit enable register

SARY — Sat, 15 May 2010 17:46:09 GMT

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

Re: CAN transmit enable register

VickLiui — Fri, 18 Jun 2010 14:27:57 GMT

you can use easily the code

CAN0TFLG = CAN0TBSEL

Re: CAN transmit enable register

VickLiui — Fri, 18 Jun 2010 14:30:22 GMT

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;

Re: CAN transmit enable register

kdn — Sun, 07 Dec 2014 04:44:51 GMT

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