PatternsSpecification(design_name, design_id, pattern_id) {
  IjtagRetargetingOptions {
    tck_period : 20ns;
  }
  Patterns(patterns_name) {
  }
}

让仿真时，相应时间port/pin有时钟产生。

PatternsSpecification(design_name, design_id, pattern_id) {
  ClockPeriods {
    aclk : 20ns;
    bclk : 20ns;
  }
  Patterns(patterns_name) {
  }
}