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Carry adder

This example defines a component with inputs a and b, and a result output. At any time, result will be the sum of a and b (combinatorial). This sum is manually done by a carry adder logic.

case class CarryAdder(size : Int) extends Component {
  val io = new Bundle {
    val a = in UInt(size bits)
    val b = in UInt(size bits)
    val result = out UInt(size bits)  // result = a + b
  }

  var c = False   // Carry, like a VHDL variable
  for (i <- 0 until size) {
    // Create some intermediate value in the loop scope.
    val a = io.a(i)
    val b = io.b(i)

    // The carry adder's asynchronous logic
    io.result(i) := a ^ b ^ c
    c \= (a & b) | (a & c) | (b & c); // variable assignment
  }
}

object CarryAdderProject extends App {
  SpinalVhdl(CarryAdder(4))
}