converting a wire value to an integer in verilog

Question

I want to convert the data in a wire to an integer. For example:

wire [2:0] w = 3'b101;

I want a method that converts this to '5' and stores it in an integer. How can I do that in a better way than this:

j=1;
for(i=0; i<=2; i=i+1)
begin
  a=a+(w[i]*j);   
  j=j*2;
end

Also, how do I convert it back to binary once I have the value in an integer? This seems a clumsy way. Thank you.

Solution 1

Easy! Conversion is automatic in verilog if you assign to an integer. In verilog, all the data types are just collection on bits.

integer my_int;
always @( w )
    my_int = w;

Solution 2

As Marty said : conversion between bit vectors and integers is automatic. But there are a number of pitfalls. They are obvious if you keep in mind that an integer is a 32 bit signed value.

• Don't try to assign e.g. a 40 bit value to an integer.
• Default bit vector are unsigned so a 32 bit vector may become negative when it is an integer.
• The opposite is also true: a negative integer e.g. -3 will become an 8 vector with value 8'b11111101

I don't know why you want to convert to an integer and back. I just want to point out that arithmetic operations are fully supported on signed and unsigned bit vectors. In fact they are more powerful as there is no 32-bit limit:

reg [127:0] huge_counter;
...
   always @(posedge clk)
      huge_counter <= huge_counter + 128'h1;

Also using a vector as index is supported:

wire [11:0] address;
reg  [ 7:0] memory [0:4095];
...
   assign read_data = memory[address];

Comments

[Brahadeesh]

thank you. I also want to do the reverse, as in w=my_int. is it allowed?

[Marty]

It is, but you'll only get the 3 LSBs of my_int stored in w. For example, if the number 'd16 (10000) is in my_int, w will become= 3'b000

[Brahadeesh]

got it. Thank you. It means I just have to take care to keep w long enough.