Sony sensors support Sequential Trigger mode. In other words, they can be triggered with sequential hardware trigger pulses. In order to achieve the maximum frame rate for these cameras when using sequential trigger pulses, they must meet certain timing requirements. For detailed information, please refer to the PL-D Timing Diagrams article. In particular the PL-D Sony Sensor Timing Diagram and its Sequential Trigger Pulses (High FPS) section.
Note: If the sequential trigger pulses do not meet the timing requirements, they will be ignored, and the cameras will output a lower frame rate. Usually, this is half of the targeted frame rate.