Trouble running picoblaze code
The problem is, that your program doesn't really end. After you've executed your two instructions the picoblaze will continue executing. Eventually the instruction pointer will overrun and your program restarts from address zero.

You need a way to halt your picoblaze. You can either do this by adding additional logic to gate the clock or put an endless loop at the end of your code like this:

;**************************************************************************************
; OUT Port definition
;**************************************************************************************
    CONSTANT sx1,           16
    CONSTANT sx2,           20
;**************************************************************************************
; Special Register usage
;***********************************************************************************
    NAMEREG SE,     TEMP1
    NAMEREG SD,     TEMP2

    OUTPUT  TEMP1,      sx1
    OUTPUT  TEMP2,      sx2

End:
    JUMP    End