code: public static byte[] createAPDU(int service, byte[] asdu)
  	{
  		if (asdu.length > 254)
  			throw new KNXIllegalArgumentException(
  				"ASDU length exceeds maximum of 254 bytes");
  		final byte[] apdu = new byte[2 + asdu.length];
  		apdu[0] = (byte) ((service >> 8) & 0x03);
  		apdu[1] |= (byte) service;
  		for (int i = 0; i < asdu.length; ++i)
  			apdu[i + 2] = asdu[i];
  		return apdu;
  	}
docs: Creates an application layer protocol data unit out of a service code and a service
  data unit.
  <p>
  The transport layer bits in the first byte (TL / AL control field) are set 0. For
  creating a compact APDU, refer to {@link #createCompactAPDU(int, byte[])}.
  
  @param service application layer service code
  @param asdu application layer service data unit, <code>asdu.length</code> &lt;
  255
  @return APDU as byte array