4.4.1.1 Extended X Data Space

The lower portion of the base address space range, between 0x0000 and 0x7FFF, is always accessible, regardless of the contents of the Data Space Read Page register. It is indirectly addressable through the register indirect instructions. It can be regarded as being located in the default EDS Page 0 (i.e., EDS address range of 0x000000 to 0x007FFF with the base address bit, EA[15] = 0, for this address range). However, Page 0 cannot be accessed through the upper 32 Kbytes, 0x8000 to 0xFFFF, of base Data Space in combination with DSRPAG = 0x00. Consequently, DSRPAG is initialized to 0x001 at Reset.

Note:
  1. DSRPAG should not be used to access Page 0. An EDS access with DSRPAG set to 0x000 will generate an address error trap.
  2. Clearing the DSRPAG in software has no effect.

The remaining PSV pages are only accessible using the DSRPAG register in combination with the upper 32 Kbytes, 0x8000 to 0xFFFF, of the base address, where the base address bit, EA[15] = 1.