I am designing a circuit where I am required to connect 32 1-bit outputs from 32 NAND gates to the input of 2 16-input OR gates. I am writing Verilog for this but unable to work out how to connect the initial 16([15:0]) bits to the input of the first OR16 and the remaining 16 ([31:16]) bits to the input of the second OR gate.

I tried this:

  or16_new o1(.orin1(xpow[15:0]), .or1out(or1w));
  or16_new o2(.orin1(xpow[31:16]), .or1out(or2w));

//where orin1 is 32 bit input to the OR16 and xpow is 32 bit wire connected to the output of 32 NAND gates. or1w and or2w are wires again, connected to the output of the 2 OR16 gates.

Compiling this returns no error in ModelSim but when using icarus, it returns the following warning -

*Port 1(orin1) of or16_new expects 32 bits, got 16. Padding 16 high bits of the port.*

And similarly for the second instance too.

So I tried

or16_new o1(.orin1[15:0](xpow[15:0]), .or1out(or1w));
or16_new o2(.orin1[31:16](xpow[31:16]), .or1out(or2w));

This returns an error, both, in ModelSim and in Icarus.

If it helps, this is how I have defined the or16_new module:

module or16_new (

input [31:0] orin1,
output or1out);

wire w9, w10, w11, w12;

nor nr_1(w9, orin1[0], orin1[1], orin1[2], orin1[3]);
nor nr_2(w10, orin1[4], orin1[5], orin1[6], orin1[7]); 
nor nr_3(w11, orin1[8], orin1[9], orin1[10], orin1[11]);
nor nr_4(w12, orin1[12], orin1[13], orin1[14], orin1[15]);
nand (or1out,w9,w10,w11,w12);
  • 1
    \$\begingroup\$ @Lan, I have seen you tried to reply by editing the question. This is not how this site works: write your answer in the field below the question, and avoid one-liners (add a short explanation and/or code example). \$\endgroup\$ Sep 13 '16 at 12:33
  • \$\begingroup\$ The error message tells you exactly where the problem is (as described in the answer below) \$\endgroup\$ Sep 13 '16 at 16:57
  • \$\begingroup\$ Why is orin1 input defined as 32 bit wide? \$\endgroup\$
    – Moberg
    Sep 14 '16 at 7:22
  • 1
    \$\begingroup\$ @dave_59 I didn't know that I could miss such a simple thing as port width. And I was trying to debug it for nearly 2 days. Thanks. Defining orin1 as input [15:0] orin1; And using the first way of instantiation, helped. \$\endgroup\$ Sep 14 '16 at 8:01

You need to define the or16_new input port as

input [15:0] orin1,

Then your first try should work.

  • \$\begingroup\$ input [15:0] orin1; \$\endgroup\$ Sep 20 '16 at 6:02

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