truncated value

Altera_Forum · ‎11-17-2010

Hi all,

when I'm designing a simple mux:

assign cmp_b = sel_ab1 ? (n+1'b1) : a;

where N = 2

I got this warning:

"Warning (10230): Verilog HDL assignment warning at determining_pivot_DU.v(69): truncated value with size 32 to match size of target (4)"

What can I do in order to eliminate this warning?

Thanks in advance,

ty6

Altera_Forum · ‎11-17-2010

I presume cmp_b and a are 32 bits wide.

Change the adder to match 32bits:

assign cmp_b = sel_ab1 ? (N+32'h00000001) : a;

You may need to modify N width, too.

Altera_Forum · ‎11-17-2010

Nope, cmp_b and a are 4 bits, but I define N as below:

parameter N = 2;

should I redefine as:

parameter N = 4'b0010 ?

Thanks

ty6

Altera_Forum · ‎11-17-2010

--- Quote Start ---

should I redefine as:

parameter N = 4'b0010 ?

--- Quote End ---

Right.

Then:

assign cmp_b = sel_ab1 ? (N+4'b0001) : a;

However these type of warnings are usually not a problem, provided you are aware of the size mismatch and its implications.

The compiler will truncate extra bits or pad with zero when missing (i.e. your "+ 1'b1" assignment on a 4bit value would be automatically converted into "+ 4'b0000")

Regards