When using the PB926EJ-S as a standalone development system, you must connect the supplied brick power supply to power socket J35 or an external bench power supply to the screw-terminal connector. See Figure 2.6.
If you are using the supplied brick power supply connected to J35, the Standby/power pushbutton toggles the power on and off.
If you are using an external power supply connected to J34, or you are powering the board from the PCI backplane, the Standby/power switch is not used and power is controlled by shutting down the external power source.
You can use only one power source for the system. Use only the PCI connector, J34, or J35. Do not, for example, use the PCI connector and J34 at the same time.