Verilog: Can you put “assign” statements within always@ or begin/end statements?

Question

Is this allowed?

input w;
     input [8:0]y;
     output reg [8:0]x;
     always@(w)
     begin


     //x[0] or A is never on in any next state
     as         


        

Answer 1

Building upon Marty's answer, you should read section 9.3 of the IEEE Verilog Standard (1364-2005, for example), where it describes "Procedural Continuous Assignment". The spec allows for assign statements within an always block. However, from my experience, it is quite rare.

Another issue with your code is that it has compile errors with two different simulators that I tried. Both generate error messages that bit-selects or part-selects cannot be used on the left hand side of the assignment.

Another possible solution is to get rid of the always block, and just use simple continuous assignments.

input w;     
input [8:0] y;
output [8:0] x;
assign x[0] = 0;     
assign x[1]= (y[0]&~w) | (y[5]&~w) | (y[6]&~w) | (y[7]&~w) | (y[8]&~w); //B     
assign x[2]= (y[1]&~w); //C     
assign x[3]= (y[2]&~w); //D     
assign x[4]= (y[3]&~w) | (y[4]&~w); //E     
assign x[5]= (y[0]&w) | (y[1]&w) | (y[2]&w) | (y[3]&w) | (y[4]&w); //F     
assign x[6]= (y[5]&w);     
assign x[7]= (y[6]&w);     
assign x[8]= (y[7]&w) | (y[8]&w);