Under what circumstances should I use 'requisite' and 'required'?

The context of this is in the writing a technical document. The statement I am writing is something of the ilk:

The package then updates the [requisite/required] number of tables.

I was wondering which is more appropriate here, and more broadly, which circumstances each should be used.

Required is a synonym of requisite (see the synonym list for requisite from the Merriam-Webster dictionary, for example).

As for the usage, it is required that is in general used in this kind of context. Compare the Google result counts:

"required number of tables" = 25,700 results 
"requisite number of tables" = 2,890 results

"required database tables" = 155,000 results
"requisite database tables" = 760 results

"required form fields" = 534,000 results
"requisite form fields" = 6 results

Moreover, it seems that in any context required is more used than requisite. The table below is from the Corpus of Contemporary American English (COCA). It shows the number of occurrences of each word (requisite as W1 and required as W2) next to other words. In all cases, required occurs more than requisite.

"Required" has more to do with a rule to be abided by irrespective of whether it is fit for the end purpose. "Requisite" means that it is needed to achieve the end purpose. e.g. "the rule requires that every room should be equipped with neon bulbs"

Are neon bulbs necessary to have light in the room? No, you could use any other type of bulbs: this is required (a requirement). In contrast, if you wanna see anything when it is dark in the room, you will need to install the requisite bulbs. Whether they be neon or else.