With Default settings -> LAGC plus peak white on.
Brightness = 00hex
Contrast = 80 hex, measurement taken using the Tektronix VM700T for white level gave Y = 234 decimal.
100IRE = 235 decimal on the VM700T.
Using manual gain with no peak white is correct setup for this investigation. Luma Manual Gain (LMG) set to C664 hex Y level = 254 decimal.
Reducing brightness to FA hex, Y level = 251 decimal. Contrast increased to FF hex, Y level = 252 decimal. Conclusion, it is not possible to achieve 254 decimal when brightness is reduced either using contrast or manual gain.
However, in the light of the above we have the ability to enable a different algorithm similar to that used on previous generations of decoders. In some instances the algorithm has limitations in regards to clipping and saturation. We do not recommend this mode or evaluate it, but it may meet your requirements.
The write sequence to enable the aforementioned algorithm is given below in hex: