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Subject: 
Extending the HB memory... I know, I know...
Newsgroups: 
lugnet.robotics.handyboard
Date: 
Tue, 24 Mar 1998 12:19:07 GMT
Original-From: 
Anthony Oren Loeppert <oren@mail+nomorespam+.utexas.edu>
Viewed: 
2517 times
  
I couldn't sleep so I thought I would make some use of my insomnia.

Several people have asked if the HB's memory can be extended, and usually
the answer is no, not if you want to run IC.  I have been taking a break
from my navigation systems, and been thinking about a SPI driven memory
extension.  I have 2, 128k SRAM chips, just lying here doing nothing so I
started wondering what it would take to build and write code to support the
device.  What I envision is a sort of harddrive for the HB.  Sure it's
slow, but to be able to dynamically load/unload stored programs or data not
always needed in main memory, it might be worth the trouble.  I was
thinking 4, 8 bit serial_in/parallel_out (HC164) strung together the memory
chips, and an 8 bit parallel in serial out(HC165).  18 bits necessary for
adressing 256k of memory, 8 for data to be written.  1 bit for read/write.
Am I leaving anything out? That still leaves 5 bits to either add a few
more bits to the addressing space for larger chunks of RAM, or control
plenty of stuff via the serial port.  The actual device _seems_ easy enough
to build, but the task of the software seems a little more daunting.  My
problem is I don't know much about how IC does it's memory management (I
guess that's what source code is for though), not much about memory
management in general.  I have a book on design of operating systems which
has some stuff about mem. man. but haven't really had chance to read it.
Does integrating this idea into IC seem riddled with problems, or does it
sound semi-reasonable?  I'm a CS major, so something like this would really
be educational. I'm not asking for help with the programming (at least not
yet), I am just trying to test the water before I jump in head first.

SO.... with all that said, if this message seems crazy, I'll blame it the
fact that I haven't slept in a long time.



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