<<<Going by your surmise on the analog comparator in AT 89c4051, looks like you dont ever need a data sheet ? >>>

No, you are wrong.
I love data sheets.
I adore data sheets.
I have thousands of datasheets in paper or electronic format.
However, sometimes they are missing or incomplete.
In this particular times, I tray to discover the trough.
When the datasheet are incomplete and I am very interested to use that circuit I generally ask for details from the manufacture.
If the manufacture does not respond ( for different reasons ) I summit the circuit to some tests in my laboratory as the manufactures would do .
I confess, in the last years, I had to do a lot of such task and I had a lot of bad surprises.
I thing it is a general trend to do more simplified data sheets as the personnel involved in this hard labor decreases.
Anyhow, you can trust my measurements.

Best regards,

Cristian