C structure help required

U8 --- 1 byte
s16---2 byte

typedef struct
{
U8 DL ;
U8 IN ;
U8/S16 Data ; /* Data*/
}Appl;

1.) As u can c the Data field i want to have can be of 1 byte or 2 bytes
please advice the type of structure i should have i don't want to have 2 structures.

2.) i want to transmit the above data through the serial port using my driver, now if the Transmission has to be in BIG ENDIAN format the High byte goes first....when i recieve the same structure back how do i know the data is One bye or 2 byte.

cool

You should either modify your structure to keep an ID flag which denotes the fact that the last variable is to be one byte instead of two, or if your "two byte" range is not using all of the bits, set one bit in the two byte range and check it to see if you're supposed to use one byte or two.

Quzah.

>>please advice the type of structure i should have i don't want to have 2 structures.
Maybe something like this would work for you, the endian flag tells you which member of the union is being used, and the union saves you from having two different memory locations for the variabls DataS and DataU.

Code:

---

typedef struct {
  U8 DL;
  U8 IN;
  unsigned endian: 1;
  union {
    U8  DataU;
    S16 DataS;
  } Data;
} Appl;

---