Dear Don Cragun,
Thank you very much for your reply.
I am using C macro to accomplish this. I can not pass states to remove from

Code:

state

as I am not aware of previous state. What I want is their should always have no more than one of the three low order bits set.
Example :- If I am in

Code:

state1

currently then my state variable would be

Code:

 xxxx x001

. Now If I want to set state to

Code:

state3

then my state variable should become

Code:

 xxxx x100.

Thank you.