If you have a program in 8051 assembly language and need to change the byte order (endian-ness) of a 16 bit variable it is rather easy to do. If the variable is stored in the 8051 internal data memory as follows:

    ...
WORD_VAL:
    DS   2
    ...
    ...
    XCH  A, WORD_VAL+0
    XCH  A, WORD_VAL+1
    XCH  A, WORD_VAL+0

This gets the job done short and sweet and even keeps the original value of the A register intact.

Michael Karas