Function modules This section contains information on the following topics:FM x50-1 Counting (S7-300, S7-400)FM 350-2 Counting (S7-300, S7-400)FM x51 Positioning (S7-300, S7-400)FM x52 Cam Controlling (S7-300, S7-400)FM 355 PID Control (S7-300, S7-400)FM 355-2 Temperature Control (S7-300, S7-400)FM 455 PID Control (S7-300, S7-400)