How to create decimal array parameter with width set by another parameter?

Question

My module has a configurable width input of signals sensor_line[WIDTH-1:0] where WIDTH is parameter. For each sensor_line I have a recorder module instantiated with a generate block in a for loop. I need to pass a decimal number parameter to this recorder which is different for each sensor_line.

I need to create some decimal array parameter to give to my module in the top, which it’s width will be aligned with the WIDTH parameter. I don’t mind if I need to match the given array size myself as long as I can do it from the top when instantiating my module.

Looking for a solution, I found only for passing an array of bits (binary value). For example, to pass 5 bits for each sensor_line, a code like this can be used:

module my_module #(
    parameter WIDTH = 4,    // number of input lines
    parameter [4:0] CYCELS [WIDTH-1:0] = '{ WIDTH{5'b0}}
)
(
    Input clk;
input [WIDTH-1:0] sensor_line;
…
);
logic [WIDTH-1:0] sensor_line_out;
…
genvar i;
generate
for (i=0; i< WIDTH; i=i+1) begin : sensor_sync
        recorder #(
            . CYCELS(CYCELS [(i+1)*5:i*5])
        )
        recorder_instance(
            .in(sensor_line[i]),
            .out(sensor_line_out[i]),
            .clk(clk),
            …
        );
    end
endgenerate
…

endmodule

How can I pass decimal values to the recorder module, not bits like in the example, like passing integer array in C and then point to the array at index [i] and at the end instance my module like this:

my_module #(
    .WIDTH(4),  // number of input lines
    .CYCELS([2,3,5,4])
) my_module_1 (
...
)

my_module #(
    .WIDTH(3),  // number of input lines
    .CYCELS([3,2,2])
) my_module_2 (
...
)

dave_59 · Accepted Answer · 2023-01-31 15:47:23Z

The syntax you used to pass an array of decimal values is incorrect. For example, change:

.CYCELS([2,3,5,4])

to:

.CYCELS('{2,3,5,4}) // an assignment pattern

or

.CYCELS({2,3,5,4})  // an unpacked array concatenation

Here is actual code that compiles:

module my_module #(
    parameter WIDTH = 4,    // number of input lines
    parameter [4:0] CYCELS [WIDTH-1:0] = '{default:'0}
);

for (genvar i=0; i< WIDTH; i++) begin : sensor_sync
    initial $display("%m CYCELS[%0d]=%0d", i, CYCELS[i]);
end

endmodule


module top;

my_module #(
    .WIDTH(4),  // number of input lines
    .CYCELS('{2,3,5,4})
) my_module_1 (
);

my_module #(
    .WIDTH(3),  // number of input lines
    .CYCELS('{3,2,2})
) my_module_2 (
);

endmodule

Output:

top.my_module_1.sensor_sync[0] CYCELS[0]=4
top.my_module_1.sensor_sync[1] CYCELS[1]=5
top.my_module_1.sensor_sync[2] CYCELS[2]=3
top.my_module_1.sensor_sync[3] CYCELS[3]=2
top.my_module_2.sensor_sync[0] CYCELS[0]=2
top.my_module_2.sensor_sync[1] CYCELS[1]=2
top.my_module_2.sensor_sync[2] CYCELS[2]=3

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