Where does the (analog digital converter) ADC obtain the analog inputs from?

Hi all,

In the CD came along with the DE0-Nano board, in the folder Demonstration>DE0_Nano_SOPC_DEMO>ip>TERASIC_ADC_READ, there are two files: ADC_READ.vhd and TERASIC_ADC_READ.v.

I have one question:

1. Where does the (analog digital converter) ADC obtain the analog inputs from? I couldn't find any values assigned to the ADC component.

Please guide, thank you, I truly need to use the Terasic_ADC_Read custom component in my VHDL system, thank you.