Systemverilog coverage point for multiple of n - system-verilog

Question

I am trying to create a bin in my coverage group to sample values that are multiple of n (where n is a constant integer in my case 15). So far, I have came
up with the following code:
class rx_port;
int unsigned rx_rates[];
...
covergroup rx_cov with function sample (int unsigned rate);
coverpoint rate{
bins no_rate = {0};
bins mul_of_15 = {SOME_PRE_DEFINED_PATTERN};
}
endgroup;
....
endclass
Where SOME_PRE_DEFINED_PATTERN is an array of int from 0 to a system macro with the step of 15. I am not sure if this is the correct/best way of generating this bin. Any better suggestion?

Answer 1

How about writing some helper functions:
module FIFTEEN;
class rx_port;
typedef enum {IS_ZERO, IS_DIVISIBLE_BY_15, IS_NOT_DIVISIBLE_BY_15} rate_type;
function new;
rx_cov=new;
endfunction
local function rate_type covergroup_helper(input int unsigned i);
if (i==0) return IS_ZERO;
if (i%15==0) return IS_DIVISIBLE_BY_15;
return IS_NOT_DIVISIBLE_BY_15;
endfunction
function sample (input int unsigned i);
rx_cov.sample(covergroup_helper(i));
endfunction
covergroup rx_cov with function sample (rate_type rate);
coverpoint rate;
endgroup;
endclass
rx_port R = new;
initial
begin
void'(R.sample(0));
void'(R.sample(30));
void'(R.sample(31));
$display("coverage R.rx_cov.get_coverage= %f", R.rx_cov.get_coverage);
end
endmodule
https://www.edaplayground.com/x/65v7
Here I've written a function that determines whether its input is divisible by 15 or not and another function which calls that to do the sampling. You could combine those functions together, but I like the division of labour in my example.

Answer 2

It turns out that there is a better way:
module FIFTEEN;
class rx_port;
function new;
rx_cov=new;
endfunction
function sample (input int unsigned i);
rx_cov.sample(i);
endfunction
covergroup rx_cov with function sample (int unsigned rate);
coverpoint rate {
bins IS_ZERO = {0};
bins IS_DIVISIBLE_BY_15 = {[1:$]} with ((item % 15)==0);
bins IS_NOT_DIVISIBLE_BY_15 = {[1:$]} with ((item % 15)!=0);
}
endgroup;
endclass
rx_port R = new;
initial
begin
void'(R.sample(0));
void'(R.sample(30));
void'(R.sample(31));
$display("coverage R.rx_cov.get_coverage= %f", R.rx_cov.get_coverage);
end
endmodule
https://www.edaplayground.com/x/3T5v
You can use with to specify bins. So
bins IS_DIVISIBLE_BY_15 = {[1:$]} with ((item % 15)==0);
gives you a bin that is hit whenever the value is divisible by 15 (but not 0) and
bins IS_NOT_DIVISIBLE_BY_15 = {[1:$]} with ((item % 15)!=0);
gives you a bin that is hit whenever the value is not divisible by 15.