Vimal Amin said:
Mov FLKEY,0xA5; // Key Sequence 1
Mov FLKEY,0xF1; // Key Sequence 2

Maybe #0A5h and #0F1h will work better ... ?

this is, probably, the most common "clerical error" (as opposed to "concept error") in '51 assembly.

as an occasional purveyor of said problem I have developed the following method

1) ALL constants are named and listed/defined at top of the module
2) a numerical value inside the body of the program is illegal.

Now, when a bug makes me start removing some of the little hair I have left, I do a search on every constant defined at the top of the module and check the list of finds (I am using CodeWright) for missing '#'s, in the case (rarer now than it once was) where a missing '#' is the culprit it is found. This is quite a bit easier with my modified definitions (not 'EA' but "SF_EA"). I have converted everything to labels that include what it is (SF_ is a SFR, GB.... is a global bit etc) which I have found invaluable in "clerical error" hunting as well.

Erik