Actually there was a problem in my code.
We have to wait 100 ns for global reset to finish.The stimulus are supplied after 100ns.But I fired them before 100ns.When I delayed the stimulus by 100ns there was data in dout.
Wrapper file fifo.v is sufficient for simulation in ISIM .
Thanks for your help
The command "add wave -r /* " does not work for ISIM.
But in the tab Sim objects all the internal signals are preset and can be added to the waveform window by just drag & drop.
I checked it.When data written became greater than it's depth then full flags goes high.
On reading one data from the full fifo the full flag goes low.