Controllers

Direct Controllers

Direct controllers provide identical functionality to Shadow controllers and you should read that guide first to understand the background here.

Direct controllers are designed to work in the case where the model for a given IP block is managed by a 3rd party and not the test engineer responsible for the given block. Often this may exist as part of a complete device model as shown here:

From the perspective of the ATD test engineer, how the model is constructed is unimportant and the main thing they need to know is what is the path to their sub-model of interest. Let’s say in our example that the model is instantiated as $model and the path to the ATD model is $model.atd.

Creation of the controller is almost identical to the example Shadow controller.

The key difference is that instead of linking the controller to a model class who’s instances it should shadow, it is instead linked to a model instance:

# lib/atd_test_block/atd_controller.rb
module ATDTestBlock
  class ATDController
    include Origen::Controller

    model path: "$model.atd"

    # ATD pattern API implementation as before
  end
end

This is where the main difference between Shadow and Direct controllers exists, the direct controller needs to be instantiated directly:

$model = SoC::Eagle.new    # Instantiates a model of the target device

atd = ATDTestBlock::ATDController.new

atd.convert(10)  # => <BitCollection>

Once instantiated the atd object above will otherwise behave identically to the Shadow controller example.

Application environments designed in this manner are a fairly recent development, and the best practices for how to build them are probably still to emerge.

However here is one approach that would work; first the top-level controller would be created and managed by the top-level test engineer:

class EagleController
  include Origen::Controller

  model path: "$model"

  # Instantiate a model whenever a new controller is instantiated
  def initialize(options = {})
    $model = Eagle.new(options)
  end

  # Instantiate an ATD controller as required
  def atd
    @atd ||= ATDTestBlock::ATDController.new
  end
end

The target would instantiate the top-level controller, not the model:

$dut = EagleController.new

The ATD API is now available within the ecosystem as per the Shadow controller example:

$dut.atd.convert(10)  # => <BitCollection>