I am seeing two different formula for calculating sysref. I don't which one is correct and why ? Please help.
fs = 245.76 MHz, K = 32, S = 1
jesd_frame_clk = fs / K = > 245.76 MHz/ 32 = 7.68 MHz
LMFC = jesd_frame_clk/ S. => 7.68 / 1 = > 7.68 MHz
SYSREF = LMFC /N where N = 1 so sysref = 7.68 MHz / 1 = > 7.68 MHz
SYSREF = fs / LCM ( 64, S*K) = > 245.76 / LCM ( 64, 1*32) = > 245.76/64 = > 3.84 MHz
A) Which formula holds true ?
B) Why should we have 64 in LCM ? How does this magic number come ? Is this an optimum number for proper wait clock period b/w each sysref and Is it applicable only for gapped and periodic sysref but not for single shot ?