thanks for ur reply . Is it really possible.
suppose i want to write continuously for more than 5 times. how long i want to make my write enable high.
Is there any possible that junk values enter the memory.
Any synchronization problem. if any means how to solve that
see the above link.It is possible to read/write the RAM without a clock.But the necessary signals like Address,Data_in etc has to be generated and supplied to the RAM block.This will need a clock.
May be you can try something like this(I am not sure about whether it will work or any possible glitches):
type RAM_t is array (0 to 255) of integer;
signal RAM_t : RAM;
process(clk)
..
for i in 0 to 3 loop
RAM(i) <= data_to_be_written(i);
end loop;
end process;
check if 4 values are written to RAM at a time.May be this is a dangerous scheme.But anyway you can check it.