( We process the 0x20 exception by pre-putting a mask in the
  (HL) we're going to write to. If it wasn't a 0x20, we put a
  0xff mask. If it was a 0x20, we put a 0x7f mask. )
: @GET,
    A 0x03 LDri, ( @GET )
    DE COM_DRV_ADDR LDdi,
    0x28 RST, JRNZ, L2 FWR ( maybeerror )
    A ORr,
    CZ RETc, ( Sending a straight NULL ends the comm. ) ;
: @PUT, ( @PUT that char back )
        C A LDrr,
        A 0x04 LDri, ( @PUT )
        0x28 RST, JRNZ, L3 FWR ( error )
        A C LDrr, ;
H@ ORG !
HL DEST_ADDR LDdi,                                    ( cont. )