Counter Issue

Hello all, I'm new to this Altera world. Nice to have this forum that we can share something. I would like to make a pluse generate after every 8 clock signal. But the result is different, later pluse is always less than expect.

Here is the code:

always@ (posedge sclk or posedge cs)

begin

if(cs)

begin

counter<=0;

flag<=0;

end

else

if(counter<8)

begin

counter <= counter +1;

flag<=0;

end

else//

begin

counter <=0;

flag<=1;

end//

end

It's funnny that if I remove the part within //..//, and use flip flop instead of pluse, the result seems correct. Could anybody help on this? Thanks.