Stratix V GX Dev Kit - Si5338 Registers

Hello,

I have an Stratix V GX Development board with two (2) Si5338 Programmable Oscillators. My project needs one of these oscillators to be programmed in 1.5 MHz. So, I search the predefined values for the registers(of Si5338) in MAX V CPLD and I cannot find them. Where are these registers? Or what is the function of I2C Protocol to communicate with Si5338.

Thanks in advance.