INT 67H 55xxH: Alter Page Map and JMP

                                                     Compatibility: EMS 4.0+ 
 Expects: AH    55H
          AL    subfn: 00H=Use page numbers in prMapInfo->wFrameLoc
                       01H=Use segment addresses in prMapInfo->wFrameLoc
          DS:SI address of an EmsMapAndJmpRec (see below)
          DX    EMM Handle (as obtained via INT 67H 4300H)
          ──────────────────────────────────────────────────────────────────
 Returns: (none)
          ──────────────────────────────────────────────────────────────────
    Info: This lets you swap some pages of executable code into memory,
          then execute that code.

    DS:SI points to a structure that identifies which pages to map and
          where to jump.  If is formatted as:

          EmsMapAndJmpRec
           Offset Size Contents
           ▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
            +0      4  pCodeAddr  FAR address to JMP
            +4      1  bPgCnt     number of pages to map
            +5      4  prMapInfo  FAR addr of an EmsMapInfoRec
                    9             size of this structure

          Depending upon AL, the wFrameLoc fields of the EmsMapInfoRec will
          contain either page numbers (usually 0-3) or segment address (for
          instance, d000H, d400H, etc).

   Notes: See INT 67H 50xxH (map multiple pages) for related info.

          This fn does not provide a mechanism to return control to the
          caller.  Use INT 67H 56xxH (map and call) to CALL rather than
          JMP.

See Also: INT 67H: EMM Services
          Extended Memory Specification (XMS)
          Interrupts and BIOS Services
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