Question on constraint randomizing an array in system verilog

[sujithad]

Hi

I have an array of 512 entries each entry being 1024 bits size.

rand bit [1023:0] entry_rand [512];

I want to constraint randomize such that each entry is non-zero but only few bits in the entry are set.

Eg: Out of 1024 bit, I need only 5 bits be set to 1 & others be 0.

Can anyone help me how to write constraint for this?

constraint entry_rand_c {
foreach (entry_rand) {
}
}

Thanks
=sd

 

[dave_59]

Re: Question on constraint randomizing an array in systemverilog

constraint entry_rand_c {
  foreach (entry_rand[i])  $countones(entry_rand[i])==5;
}

See https://electronics.stackexchange.com/questions/36512/system-verilog-constraints

 

[sujithad]

Re: Question on constraint randomizing an array in systemverilog

Hi Dave,

Thanks. But when run on IUS, I get this error
*E: A 'system task/function call' cannot be used within a constraint expression.

Is there a workaround for this?

constraint entry_rand_c {
  foreach (entry_rand[i])  $countones(entry_rand[i])==5;
}

See https://electronics.stackexchange.com/questions/36512/system-verilog-constraints

 

[mrflibble]

Re: Question on constraint randomizing an array in systemverilog

Thanks. But when run on IUS, I get this error
*E: A 'system task/function call' cannot be used within a constraint expression.

Is there a workaround for this?

Read **broken link removed** that is down for SQL maintenance at the moment. One can only hope they are upgrading to MariaDB.