Posts: 260
Threads: 32
Joined: Jul 2005
The relative addressing of the 9825 is different from the 9835/45. You will find in the patent of the 9825 two modes of relative addressing selected by the CPU pin RELA. To quote one of the developers of the 9825:
Quote:
to answer your first question regarding
the function of RELA, it's a hardware selection
used to determine Absolute vs Relative addressing
mode calculation, tied low in the hp9825 to
accomodate code destined for rom's (allows access
to any word within a page), the pin is tied high
in hp9835/45 to accomodate relocatable code
segments.
And to be quoted further:
Quote:
there is a binary that i wrote for the 9825
that implements a bpc assembler and reverse
assembler that proved to be very useful at
the time, also, after meeting up with steve
i put some work into creating a macro package
for TeX that aims to implement a modern
assembler for the bpc source so that the
listing files (that i have in paper form)
can be reproduced
After a discussion about the 9825 on this forum, this developer contacted me and answered many of my quesions. I think these details will eventually show up on hp9825.com.
There is a useful simulator of the 9825 available from one of our forum members.
