Plot[-(Log[x]/Log[2]), {x, 0, 512}, PlotRange -> {-512, 0}, AspectRatio -> 1, ImageSize ->Medium]

lot[-(Log[x]/Log[2]), {x, 0, 32}, PlotRange -> {-32, 0}, AspectRatio -> 1, ImageSize ->Medium, GridLines->{{},Range[-6, -1]}, Filling->Bottom]