Synchronous adder

This example creates a Component out of sequential logic that does some simple arithmetic on 3 operands.

The test bench performs the following steps 100 times:

Initialize a, b, and c to random integers in the 0..255 range.

Stimulate the DUT’s matching a, b, c inputs.

Wait until the simulation samples the DUT’s signals again.

Check for correct output.

The main difference between this example and the Asynchronous adder example is that this Component has to use forkStimulus to generate a clock signal, since it is using sequential logic internally.

import spinal.core._
import spinal.core.sim._

import scala.util.Random


object SimSynchronousExample {
  class Dut extends Component {
    val io = new Bundle {
      val a, b, c = in UInt (8 bits)
      val result = out UInt (8 bits)
    }
    io.result := RegNext(io.a + io.b - io.c) init(0)
  }

  def main(args: Array[String]): Unit = {
    SimConfig.withWave.compile(new Dut).doSim{ dut =>
      dut.clockDomain.forkStimulus(period = 10)

      var resultModel = 0
      for(idx <- 0 until 100) {
        dut.io.a #= Random.nextInt(256)
        dut.io.b #= Random.nextInt(256)
        dut.io.c #= Random.nextInt(256)
        dut.clockDomain.waitSampling()
        assert(dut.io.result.toInt == resultModel)
        resultModel = (dut.io.a.toInt + dut.io.b.toInt - dut.io.c.toInt) & 0xFF
      }
    }
  }
}