c bit access union
typedef union a429_tag { // define a union of structs and/or raw data types
// struct to access each bit individually
struct {
unsigned int
bit0 : 1, bit1 : 1, bit2 : 1, bit3 : 1,
bit4 : 1, bit5 : 1, bit6 : 1, bit7 : 1,
bit8 : 1, bit9 : 1, bit10 : 1, bit11 : 1,
bit12 : 1, bit13 : 1, bit14 : 1, bit15 : 1;
};
// struct to access range of bits by name
struct {
unsigned int
label : 8,
sdi : 2,
data : 3,
ssm : 2,
parity : 1;
};
// int type to access to the entire word as an integer
unsigned int word : 16;
} a429_type;
/* Example usage */
int main() {
a429_type myUnion;
myUnion.parity = 1;
if (myUnion.bit15 == 1) {
printf("parity and bit15 refer to the same bit");
}
return 0;
}
Here is what the above code is Doing:
1. Define a union called a429_type.
2. Define a struct called bit_struct that allows you to access each bit individually.
3. Define a struct called label_struct that allows you to access a range of bits by name.
4. Define an int type called word that allows you to access the entire word as an integer.
5. Create a variable called myUnion of type a429_type.
6. Set the parity bit to 1.
7. Check if the parity bit is set.
