SimpleALU.scala

// See LICENSE.txt for license details.
package TutorialExamples

import Chisel._

class BasicALU extends Module {
  val io = new Bundle {
    val a = UInt(INPUT, 4)
    val b = UInt(INPUT, 4)
    val opcode = UInt(INPUT, 4)
    val out = UInt(OUTPUT, 4)
  }
  io.out := UInt(0) //THIS SEEMS LIKE A HACK/BUG
  when (io.opcode === UInt(0)) {
    io.out := io.a //pass A
  } .elsewhen (io.opcode === UInt(1)) {
    io.out := io.b //pass B
  } .elsewhen (io.opcode === UInt(2)) {
    io.out := io.a + UInt(1) //increment A by 1
  } .elsewhen (io.opcode === UInt(3)) {
    io.out := io.a - UInt(1) //increment B by 1
  } .elsewhen (io.opcode === UInt(4)) {
    io.out := io.a + UInt(4) //increment A by 4
  } .elsewhen (io.opcode === UInt(5)) {
    io.out := io.a - UInt(4) //decrement A by 4
  } .elsewhen (io.opcode === UInt(6)) {
    io.out := io.a + io.b //add A and B
  } .elsewhen (io.opcode === UInt(7)) {
    io.out := io.a - io.b //subtract B from A
  } .elsewhen (io.opcode === UInt(8)) {
    io.out := io.a < io.b //set on A less than B
  } .otherwise { 
    io.out :=  (io.a === io.b).toUInt() //set on A equal to B
  }
}

class SimpleALU extends Module {
  val io = new Bundle {
    val a      = UInt(INPUT,  4)
    val b      = UInt(INPUT,  4)
    val opcode = UInt(INPUT,  2)
    val out = UInt(OUTPUT, 4)
  }
  io.out := UInt(0) 
  when (io.opcode === UInt(0)) {
    io.out := io.a + io.b //ADD
  } .elsewhen (io.opcode === UInt(1)) {
    io.out := io.a - io.b //SUB
  } .elsewhen (io.opcode === UInt(2)) {
    io.out := io.a  	     //PASS A
  } .otherwise {
    io.out := io.b        //PASS B
  }
}

class SimpleALUTests(c: SimpleALU) extends Tester(c) {  
  for (n <- 0 until 64) {
    val a      = rnd.nextInt(16)
    val b      = rnd.nextInt(16)
    val opcode = rnd.nextInt(4)
  // for (a <- 0 until 16) {
    // for (b <- 0 until 16) {
      // for (opcode <- 0 until 4) {
        var output = 0
        if (opcode == 0) {
          output = ((a+b) & 0xF)
        } else if (opcode == 1) {
          output = ((a-b) & 0xF)
        } else if (opcode == 2) {
          output = a
        } else {
          output = b
        }
        poke(c.io.a, a)
        poke(c.io.b, b)
        poke(c.io.opcode, opcode)
        step(1)
        expect(c.io.out, output)
  }
      // }}}
}