凿子不能重新指定为只读。

Question

这是我提出的另一个问题的延续：Instanciation of a class doesn't work (Chisel/Scala)

实际上，我想打印“结果”变量。我编写了以下命令: sbt测试，我不理解这个错误：

"chisel3.internal.ChiselException:无法重新分配到只读组合Tausworthe.b: OpResultUInt<32>“

这是测试文件

import chiseltest._
import org.scalatest.freespec.AnyFreeSpec


class combined_test extends AnyFreeSpec with ChiselScalatestTester {
  "combinedTauswhore" in {

    test(new combinedTausworthe() ){ c =>
      //Initialisation
       c.clock.step(1)
      println(c.result)

      c.clock.step(1)
      println(c.result)

    }

  }

}

这是一堂课：

import chisel3._

 class combinedTausworthe extends Module{
   val io = IO(new Bundle {
   })
   val seed1 = RegInit(322769304.U(32.W))
   val seed2 = RegInit(424235419.U(32.W))
   val seed3 = RegInit(212119443.U(32.W))
   var result= 0.U

   var b = ((seed1 << 13)(31,0) ^ seed1)
   seed1 := ((seed1 & 4294967294L.U) << 12)(31,0) ^ b
   b := ((seed2 << 2)(31,0) ^ seed2) >> 25
   seed2 := ((seed2 & 4294967294L.U) << 4)(31,0) ^ b
   b := ((seed3<<3)(31,0) ^ seed3) >> 11
   seed3 := ((seed3 & 4294967294L.U) <<17)(31,0) ^ b

   result := (seed1 ^ seed2 ^ seed3)
   

 }

object Main extends App {
 
}

Answer 1

在Chisel3中，:=是驱动具有某种值的信号的连接操作符。把它想成是制造一种电气连接。在您的代码中，您似乎试图将变量重新分配到可变变量，而不是使用值驱动该变量的值，尝试=。

import chisel3._

class combinedTausworthe extends Module{
  val io = IO(new Bundle {
  })
  val seed1 = RegInit(322769304.U(32.W))
  val seed2 = RegInit(424235419.U(32.W))
  val seed3 = RegInit(212119443.U(32.W))
  var result= 0.U

  var b = ((seed1 << 13)(31,0) ^ seed1)
  seed1 := ((seed1 & 4294967294L.U) << 12)(31,0) ^ b
  // Note using assignment (=), not connection (:=)
  b = ((seed2 << 2)(31,0) ^ seed2) >> 25
  seed2 := ((seed2 & 4294967294L.U) << 4)(31,0) ^ b
  b = ((seed3<<3)(31,0) ^ seed3) >> 11
  seed3 := ((seed3 & 4294967294L.U) <<17)(31,0) ^ b

  // Same thing here
  result = (seed1 ^ seed2 ^ seed3)   
}

尽管如此，由于Scala是一种函数式编程语言，我们在风格上更喜欢纯/不变的结构，所以只使用值：

import chisel3._

class combinedTausworthe extends Module{
  val io = IO(new Bundle {
  })
  val seed1 = RegInit(322769304.U(32.W))
  val seed2 = RegInit(424235419.U(32.W))
  val seed3 = RegInit(212119443.U(32.W))
  // Note result var removed and replaced with val below

  val b1 = ((seed1 << 13)(31,0) ^ seed1)
  seed1 := ((seed1 & 4294967294L.U) << 12)(31,0) ^ b1
  val b2 = ((seed2 << 2)(31,0) ^ seed2) >> 25
  seed2 := ((seed2 & 4294967294L.U) << 4)(31,0) ^ b2
  val b3 = ((seed3<<3)(31,0) ^ seed3) >> 11
  seed3 := ((seed3 & 4294967294L.U) <<17)(31,0) ^ b3

  val result = (seed1 ^ seed2 ^ seed3)
}