why the I/O output port is not right?

hi:everybody! i met a very strange phenomenon!

i define a bidir port named daccontrol[1..0],then i write the direction register so that i could define it as a output port, THEN I OUTPUT A "1" TO daccontrol[1]

or daccontrol[0],in theory one of them should be3.3v ,another should be 0v,BUT BOTH OF THEM SHOW 2V!

I have tried many times! when i write "1" to both daccontrol[1] and daccontrol[0],they show right! so is the data[0]!

thanks !! with my regards!