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GPAGE question

Question asked by H?kan Dahlberg on Feb 3, 2011
Latest reply on Feb 3, 2011 by H?kan Dahlberg

Hi,

 

I'm trying to migrate some code from S12C to S12XDT256. I have a memory read function that  takes a pointer to far pointer as argument, loads a and transmits a series of CAN messages with four bytes of data together with the address of the first byte in each message.

 

 

// Read consecutive bytes from memory on same pagestatic void ReadMem( dword *far *ppFarAddress, word len ){  _CANSTR CanTxMsg;  CanTxMsg.Byte.Idr0 = READ_MEM_ECHO_MSG;    while (len != 0)  {    *(dword *far *)&CanTxMsg.Array[CAN_DB0] = *ppFarAddress;  // copy address    *(dword *)&CanTxMsg.Array[CAN_DB3] = **ppFarAddress;      // copy 4 bytes data    if (len > 3)    // full msg?    {      CanTxMsg.Byte.Dlc.U8 = 7;      len -= 4;     // remaining bytes      *ppFarAddress += 1;         // point to next address    }    else                          // last msg   {     CanTxMsg.Byte.Dlc.U8 = len + 3;     len = 0;     // done   }   CanSendMsg( &CanTxMsg );   KickDog();   DelayXus(8000);    // 8 ms intermission between transmissions.  }}

 

Problem:

This code works fine in the S12C, but in S12XDT256, I can see from the assembly listing that GPAGE gets involved, which as far as I can tell is read only in bit 7. Anyways the messages are not transmitting the expected data, but the address reads ok. Guess I don't understand the concept of GPAGE.

 

Any help appreciated, thanks.

 

Håkan

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