Area

Sometime, creating a Component to define some logic is overkill :

Need to define all construction parameters and IO (verbosity, duplication)
Split your code (more than needed)

For this kind of cases you can use Area to define a group of signals/logic.

class UartCtrl extends Component {
  ...
  val timer = new Area {
    val counter = Reg(UInt(8 bit))
    val tick = counter === 0
    counter := counter - 1
    when(tick) {
      counter := 100
    }
  }

  val tickCounter = new Area {
    val value = Reg(UInt(3 bit))
    val reset = False
    when(timer.tick) {          // Refer to the tick from timer area
      value := value + 1
    }
    when(reset) {
      value := 0
    }
  }

  val stateMachine = new Area {
    ...
  }
}

Tip

Abuse of area !

No more toto_a, toto_b, toto_c as it so often done in common HDL, any Component‘s internal module could be an Area

Note

ClockingArea are a special kind of Area which allow to define chunk of hardware which use a given ClockDomain