Almpost alwauys, if you have two bytes of data that combine into one 16-bit value there will be an understood normal way that the two bytes are paired high and low at memory addr and addr+1.

In the case when one byte is actually broken into two characters, such as two ASCII digits characters that represent an alternate coding for the binary representation of a number, then the "order of which is high and which is low" is almost completely context sensitive and may very well be completely up to the programmer to select a method of handling the data and extending a uniform intrepertation of the method throuought his project.
Michael Karas