进位加法器

此示例定义了一个具有输入 a 和 b 以及输出 result 的组件。在任何时候， result 将是 a 和 b （组合逻辑）的和。该和是由进位加法器手动完成的。

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))
}