Struct in union

Hi
I have some problems with struct inside a union
This is my code.

union{
	unsigned char id_byte[2];

	struct {
			unsigned char DLC:4;
			unsigned char RTR:1;
			unsigned int identifier:11;
			}del_element;
}can_descriptor;

when I write an_descriptor.del_element.identifier=0x0A;

nothing comes in id_byte array why?
The values I put in DLC and RTR are placed correct.

If i change the code to
union{
	unsigned char id_byte[2];

	struct {
			unsigned int identifier:11;
			unsigned char DLC:4;
			unsigned char RTR:1;
			}del_element;
}can_descriptor;
And writes 0x0A to identifier:
id_byte[0]=0
id_byte[1]=0x0A

but i shoud be
id_byte[0]=0x80
id_byte[1]=0x01

why?
This program is part of an CAN program for SJA1000, this funktion i made make it easy to write the CAN iddentifiers DLC and RTR bit in the controller.....if it worked.

Best Regrads
Soren

Parents Reply Children
No data
More questions in this forum