|Re: The MOARP (a "concept module"... wouldn't it be nice?)|
Message #5 Posted by Diego Diaz on 18 Oct 2008, 11:09 p.m.,
in response to message #4 by Egan Ford
Well, you're "playing major leagues"... :-)
While reading from a microSD (or SD for that matter) card is "reasonably" easy, writing is not trivial.
The core memory inside these devices is just a Flash memory cell array; and this kind of memory requires of an "erase" cycle prior writing.
Such erase cycle clears the contents of a whole sector (64, 256,... bytes) thus, in order to write a single byte/word you must first read the whole sector into some temporary buffer, then modify the required byte(s), erase the whole sector, and finally re-write the updated contents.
All this process can of course be done by the microcontroller... but it cannot be achieved fast enough to cope with HP-41 bus timing requirements.
Sorry for the bad news. As the title shows, the concept is having access to all the *ROM* pacs in a snap. However, procedures like the one used by RAM2ROM.HEX on NoVRAM, can be build to allow sort of back-up copies.
Regrettably, my knowledge on M-code is so limited that handling user RAM, Extended Memory or Focal programs and moving them back and forth is far from my scope... :-(
Some M-code gurus out there may be interested in the project though... any volunteers? :-)
Thanks for your comments and best wishes.