Paul;  I remember this issue over safe use of high and low bank naming in
assembly, so I asked the supreme professor, Andrew Warren.  His answer to me
is below.
Chris Eddy


    Hi, Chris.

    Actually, I DISCOURAGED the practice of doing the XOR in the
    file-register equate; here are the four methods that are
    commonly used, along with my reasons for using Method #4 over
    the others:

    Note:  In the following examples, "XXX" is a register address
           on page 1 (i.e., between 0x80 and 0xFF).

    METHOD 1:

        REG     EQU     XXX-128         ;Generates no warnings, but
                ....                    ;also doesn't allow REG to
                MOVWF   REG             ;be viewed in MPASM watch
                                        ;windows.  Equivalent to:
                                        ;    REG EQU XXX & 0x7F
                                        ;    and
                                        ;    REG EQU XXX ^ 0x80
                                        ;both of which have the same
                                        ;problem.

    METHOD 2:

        REG     EQU     XXX             ;Generates an MPASM warning.
                ....                    ;
                MOVWF   REG             ;

    METHOD 3:

        REG     EQU     XXX             ;Generates no warning, EVEN
                ....                    ;when accidentally used with
                MOVWF   REG & 0x7F      ;a page-0 register.

    METHOD 4:

        REG     EQU     XXX             ;Generates no warning when
                ....                    ;used correctly (i.e., when
                MOVWF   REG ^ 0x80      ;REG is on page 1), but DOES
                                        ;generate a warning when
                                        ;accidentally used with a
                                        ;page-0 register.