Hi Anand,
If you refer to the Parallel Peripheral Interface chapter (Chapter 11) of the BF538 Hardware Reference Manual it explains that "The state of PPI_FS3 depends completely on the state of PPI_FS1 and/or PPI_FS2, so PPI_FS3 has no inherent programmability".
The code sketches, available via 'Help: Browse Examples' (select "Code Sketch" from the 'Type' drop-down, then search the term 'PPI') list the basic API that should be called.
Beyond that, I recommend referring to this chapter for the default settings (reset values) of the PPI registers. You should then use the adi_ppi_*** commands that configure your requirements that differ from the default. For example, bit 1 of the PPI_CONTROL register is the PORT_DIR and sets either Rx or Tx mode. It defaults to 0, which is Rx mode, so if you intend to transmit over PPI you should call the adi_ppi_SetDirection() API to set it to Tx.
You can find the BF538F Hardware Reference Manual at the link below.
http://www.analog.com/blackfin/manuals
Regards,
Craig.