7730 addressing question

[dhardin at ovec.com]

Got a question.....not a critical one, .....I'm hacking a v6 730 eprom and
I noticed some jump instructions to an address range outside the Eprom
around $5100.  I realize that some of the addressing can be confusing
because of the way the eprom reader put the address range compared to the
computer, but that is not the case here.  It is actaully literally calling
the $5100 range.  The Eprom goes from $8000 to $FFFF.  My question is:  are
they running the 68hc11 in a mode where it has some internal subroutines
and memory,  or is somewhere else in the program some subroutines being
written into this space and then executed.   Has anyone seen this before?