////////////////////////////////////////////////////////////////////////
//
// can_set_mode
//
// This function first sets three most significant bits (reqop2:reqop0)
// to the mode given through the argument.  The modes can be
//
// mode
//
// 1xx  -> Configuration Mode
//             This mode allows the user to configure the Control Registers,
//            the Acceptance Mask Registers and the Acceptance Filter
//            Registers.
//
// 011  -> Listen Only Mode
//            This mode allows the PIC microcontroller to listen to the
//            bus but not actually write to it.
//
// 010  -> Loop Back Mode
//            This mode allows to the transmission of data directly from
//            the Transmission Buffers to the Recive Buffers without
//            actually driving any data to the bus
//
// 001  -> Dissable Mode
//            This mode prefents the PIC microcontroller from transmitting
//            and reciving, however the WAKIF interrupt is still active
//
// 000  -> Normal Mode
//            This is the normal mode of opperation for the CAN bus.  It
//            will recive all messages and is the only mode in which
//            data can be transmitted.
//
//   The reqop bits do not immediatly change the mode of operation, the
// three most significant bits in the CANSTAT register (opmode2:opmode0)
// must change to reflect the actuall change in mode, therefore a while
// statement is used to check if the CANSTAT opmode bits have changed to
// reflect the passed in mode
//
// More information can be found in the PIC18F4580 datasheet section 23.3
////////////////////////////////////////////////////////////////////////
void can_set_mode(CAN_OP_MODE mode) {
   CANCON.reqop=mode;
   while( (CANSTAT.opmode) != mode );
}