what's wrong between QII6.1 and QII9.0

[Altera_Forum]

wire a_cs_n; 

wire b_cs_n; assign a_cs_n = (addr[19:18]==2'b01)? 1'b0 : 1'b1; assign b_cs_n = (addr[19:18]==2'b00 && addr[17:16]==2'b10) ? 1'b0 : 1'b1; assign dout = ({16 {a_cs_n}} | 16'haaaa ) & ({16 {b_cs_n}} | 16'hbbbb) ;  With QII 6.1,dout can get 16'haaaa or 16'hbbbb.But with Qii 9.0,dout cannot get 16'haaaa。 We don't change the code.But get the different result. Why? Thank you very much!

[Altera_Forum]

--- Quote Start ---  wire a_cs_n; wire b_cs_n; assign a_cs_n = (addr[19:18]==2'b01)? 1'b0 : 1'b1; assign b_cs_n = (addr[19:18]==2'b00 && addr[17:16]==2'b10) ? 1'b0 : 1'b1; assign dout = ({16 {a_cs_n}} | 16'haaaa ) & ({16 {b_cs_n}} | 16'hbbbb) ;  With QII 6.1,dout can get 16'haaaa or 16'hbbbb.But with Qii 9.0,dout cannot get 16'haaaa。 We don't change the code.But get the different result. Why? Thank you very much!  --- Quote End ---    Hi,  I run a test with Quartus II 9.0 (Full version). I looks pretty in my project. I have the project attached. Maybe I made a mistake in the project ?  Kind regards  GPK

[Altera_Forum]

Why don't you write: 

always @ (*) begin  if (a_cs_n) dout <= 16'haaaa;  if (b_cs_n) dout <= 16'hbbbb; end