Constrained Randomization and Reproducibility

Generate varied protocol-correct transactions and reproduce a failure exactly.

Random, but valid

Constrained randomization generates combinations within a defined space. It does not replace the verification plan. It explores more interactions than a short list of directed tests.

class dma_request;
  rand bit [31:0] address;
  rand int unsigned length;
  rand bit write;
 
  constraint legal_length {
    length inside {[1:256]};
  }
 
  constraint aligned_address {
    address[1:0] == 2'b00;
  }
 
  constraint boundary {
    address[11:0] + length <= 4096;