Incometax refund for ay 2011-12

Dear Sir/ Madam

Sub: TDS refund on IT Return filed for AY 2011-12

       With Ref to above subject, I filed e-returned for AY 2011-12 as on 26/03/2012 and date of ACK received on 13/04/2012

and i seen Status of e-filing proccessing as 15/08/2012. not yet TDS refunded or AO u/s 143(1) received in my mail. please help me out of what is the timelimit for refund of TDS amount for AY 2011-12. usually it takes 3 months but in this case so delayed. why ?