Do i need to configure the regs for the first time too. or by default it has some frequency ?
You can see the internal registers of the demodulator using the LTC5594 QuikEval GUI.
A quick-start guide can be found here: https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/DC2645AF.PDF
Consider also reading the Manual for the Serial Controller used to test your board: https://www.analog.com/media/en/dsp-documentation/evaluation-kit-manuals/dc590bf.pdf
For any further questions, please redirect your thread to the appropriate sections: