CODEWITHSUNDEEP
concatenationparameter-passingsystem-verilog
Snigdha203
Snigdha203

Reputation: 101

Passing Array of Parameters through Module in System Verilog

I was trying to create arrays of parameter approx and approx1 for dct8p_v5 module in system verilog. 'kcn' module has size of 6 parameter array named 'approx'. I want to pass 3 variable from 'approx' and 3 variable from 'approx1'. I tried to concatenate these two but parameter values are not propagating into kcn module. Is the syntax is correct for passing parameter array? Please let me know!

Thanks,

Farhana 

module dct_8p_v5 #(parameter nb=18) (input [nb-1:0] xin [0:7] ,
                                  output [nb-1:0] xl2 [0:7]);
localparam integer approx [0:28]={3,1,1,3,0,0,0,0,3,3,1,2,0,7,7,0,7,7,3,
 3,3,10,9,9,7,7,10,9,9};
localparam integer approx1 [0:10]={8,8,8,8,8,8,9,8,8,16,16};
wire [nb-1:0] xl1 [0:7];
...
..
kcn  #(.n(nb), .approx({approx[12:14],approx1[0:2]})) kcn11(.x0(xl1[4]),.x1(xl1[7]),
.y0(xl2[4]),.y1(xl2[7]));
...
..
module kcn (x0,x1,y0,y1);
parameter n=10  ;
input [n-1:0] x0;
input [n-1:0] x1;
output [n-1:0] y0;
output [n-1:0] y1;
parameter integer approx [0:5]='{0,7,7,8,8,8};

Upvotes: 4

Views: 6640

Answers (3)

Greg
Greg

Reputation: 19094

IEEE Std 1800-2012 § 7.4.3 Operations on arrays states all arrays, packed or unpacked, can read and write to a slice of the array. There is a direct example in the LRM § 7.4.6 Indexing and slicing of arrays. However, not all simulators, synthesizers, etc., support slicing of the unpacked array. If .approx({approx[12:14],approx1[0:2]})) doesn't work, then try the expanded form: .approx('{approx[12],approx[13],approx[14],approx1[0],approx1[1],approx1[2]}) or .approx({approx[12],approx[13],approx[14],approx1[0],approx1[1],approx1[2]})

{} vs '{} for unpacked arrays described in IEEE Std 1800-2012 § 10.10 Unpacked array concatenation with examples in § 10.10.1

module dct_8p_v5 #(parameter nb=18) (
    input  [nb-1:0] xin [0:7] ,
    output [nb-1:0] xl2 [0:7] );
localparam integer approx [0:28] = '{3,1,1,3,0,0,0,0,3,3,1,2,0,7,7,
                                     0,7,7,3,3,3,10,9,9,7,7,10,9,9};
localparam integer approx1 [0:10] = '{8,8,8,8,8,8,9,8,8,16,16};
...
kcn  #(.n(nb),
       //.approx({approx[12:14],approx1[0:2]})
       .approx('{approx[12],approx[13],approx[14],approx1[0],approx1[1],approx1[2]}) // Alt
     ) kcn11(
         .x0(xl1[4]), .x1(xl1[7]), .y0(xl2[4]), .y1(xl2[7]));
...

Upvotes: 0

adiles
adiles

Reputation: 55

According to clause 10.9 (IEEE1800-2012 LRM)'s description of assignment patterns:

When an assignment pattern expression is used in a right-hand expression, it shall yield the value that a variable of the data type would hold if it were initialized using the assignment pattern....

Each expression item shall be evaluated in the context of an assignment to the type of the corresponding element in the array.

So for unpacked arrays the assignment is only legal when the LHS expression's number of elements matches those in its corresponding RHS expression. In your example the LHS is a single variable expecting 6 unpacked array elements whereas the module arguments are a slice of two unpacked array variables with 3 elements each.

To get around this, I recommend using bit-stream casting in the following manner. 1) Declare the parameter a packed array.
2) For the module instance's arguments, apply a bit-stream cast to each of the sub-expressions, concatenate the result, and enclose it in an assignment pattern expression. If enclosing in an APE doesn't work, bit-stream cast the concat.

Casting in this manner requires declaring user-defined types that are size-equivalent to the integrals being casted.

Upvotes: 0

dave_59
dave_59

Reputation: 42623

Your code should have worked, but the array concatenation syntax has gone through a number of rule changes throughout the different revisions of the standard. You should check with your tool vendor for the current level of support of array concatenation.

Upvotes: 1

Related Questions