Looking in the DS280MB810 Programmers' Guide, October 2016 (which is assumed still the current version), I see in Section 6.3, Adjust Signal Detect Threshold on p.14-15, that each voltage range cited (which are in fact just typical range values) has a spread of 3:1 or more. Is such a wide range due to variation of the threshold under various operating conditions, such as per the range of serial datarates supported, as well as temperature and Vcc? Which influence(s) exert the most effect on causing the threshold to vary significantly? What sort of spread could be expected over the full supported range of operating conditions (Vcc and temperature)?
Further, please provide insight into where in each of the six ranges typical thresholds would occur for very low frequency signaling, such as in the range of 10-50MHz. Please also confirm that the IC should have no difficulty in passing such low frequency signaling through, either as continuous square waves, or as an individual pulse as short as two cycles, or such a pulse repeated as infrequently as every 250 milliseconds (with squelch (0V differential signal) occurring between successive pulses).
Related to the above and looking further in the Programmers' Guide and searching for all text matches to "SD_" (thus related to Signal Detect functionality), there were found the SD_REF_HIGH and SD_GAIN register bits (p.31), with however no explanation anywhere in the document regarding what they do and what effect they have (except for the note that SD normal operation results when both bits are true). Since understanding all SD-related capabilities of the part is critical in the application here, and particularly since the threshold ranges cited (p.14-15) may all be too high for the application, please provide detailed information regarding these currently-mysterious control bits.