How do I communicate with SPI/SCI?

Hi guys,

I am currently trying to create a very simple MP3 player using the VS1011 MP3 Decoder and the PIC16LF877 Microcontroller as well as an SD card adaptor.

When using the PIC as a master and the VS1011 as a slave I need to use "SCI" in order to set up various registers so that the VS1011 is in the correct mode, has the correct volume etc. I also need to send the music data through the "SPI" interface.

My question is, how do I tell the VS1011 to change interface so that it knows I am using SCI or SDI?

By looking at the data sheet (page 1) we see the pins used to communicate:

DREQ (output)
SO (Output)
SI (input)
SCLK (input)
XCS (input)
XDCS (input)

I think I understand what all pins do other than the XDCS pin. Is this the pin that I have to set high in order to communicate using SDI? (in New Mode) as shown on page 16? (assuming that SM_SDISHARE = 0)

The VS1011 data sheet is found here: https://www.vlsi.fi/en/products/vs1011.html

I understand that the XDCS pin should be tied to Vdd as it is not required in your application from what I can tell. The XCS pin is what is used by you to tell the part when you are sending SCI (Control) commands or SDI (Data).