The Layer Alpha register specifies the per layer alpha blending value used for blending this layer with the underlying layer. The value of this register has a range from 0 which is fully transparent, to 256 which is fully opaque. Layer alpha blending is only supported when the Enable Global Alpha field in the Vivado IDE is enabled for a particular layer. When alpha blending is disabled for a layer, layers are blended as fully opaque on top of the underlying layer.