I would like to program the SPI (LE, Data and CLK) for the HMC765LPCE by using FPGA. I would like to achieve the output frequency of the PLL at 7912.5 MHz, is it correct to let R=1, Nint=158, and the Nfrac=2^22? How does HMC765 identify if I would like to program register 03H? This is not explained either in the datasheet or the operating guide. For ADF4108, it can identify which register to write given the control bits of C2,C1. Can you elaborate more on this for HMC765?
It looks like you might be using a PFD frequency of 50MHz as 50MHz * 158 = 7900MHz.
The remaining 12.5MHz is 25% of your PFD frequency and there are 24 fractional bits so Nfrac is determined by using 12.5MHz / 50MHz = 0.25 * 2^24 = 4194304 (or 2^22).
The user guide which can be found on the 'Full Product Page' for the HMC765 should help you with programming your FPGA.
Thank you Marty. I have 1 more question regarding the data format in programming the SPI.