Verilog-AMS defines hierarchical parameters $xposition and $yposition as well as $angle to express physical location and orientation as on a wafer or PCB. According to the LRM, $angle is supposed to mean “counter-clockwise”.

Our interpretation of counter-clockwise follows when choosing the x axis pointing to the right, and the y axis pointing upwards. Now a 90 degree rotation moves the x axis to the y axis, in other words (x,y)=(1,0) to (0,1). Equivalently, the y axis may be thought of as the imaginary axis in the complex plane. Then, rotation by 2\pi\phi corresponds to multiplication by exp(2\pi\phi * i), with the imaginary unit i.

This seems relevant when moving on to schematics. Since Verilog-AMS is governed by physical semantics, we retain this choice of angle and coordinates also for schematic drawings, even though other coordinate systems are in common use.

If you prefer a y axis pointing downwards, you may use a flipped coordinate system locally, as within the body of the following module. As expected, any uses of angle inside the body will be applied before the final vflip.

(* S0_vflip=-1 *)
module upside_down_module();
  [..]
endmodule  

(todo)