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Hi all, We are designing one system in which we are using TPS65987D pd controller..We have one usb type c plug( male) connector which gets connected to the mobile...also we have usb type c receptacle which is used for charging purposes...we have one battery charger and battery along with it.... Operation: if the battery is full the pd controller ( present on our board) should act like source and delivers power to the usb type c plug(mobile pd controller acting as sink)...if the battery is low, mobile pd controller should act as source i.e mobile should delivers power to our board( our board pd controller should act as sink)... Whether this communication takes place automatically in pd controller or do we need to take care using an external microcontroller?

Maybe you can get inspired by this simple elementary circuit:

Note that Vmain is a sawtooth voltage, in order to simulate a failure of Vmain to supply the required voltage. When it falls to zero (even before, in fact), Vbackup kicks in automatically. Next, when Vmain comes back to life, Vbackup disconnects itself, automatically.

Just a PMOS and a diode. The LED, and its resistor, simulate the "load" of the circuit. The Amp-meter are there only to show which source effectively supply the current. The pulldown resistor may not be required in every cases, but in general, it is, and in order to minimize the energy lost, should be of a large ohmic value.