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Saving the state of HP41 CL to PC
12-31-2017, 03:25 AM
Post: #21
RE: Saving the state of HP41 CL to PC
(12-28-2017 03:46 AM)PeterP Wrote:  [*]Which events/functions clear the RAM page at 0x800?
[*]Do I need to save the page 804 as well or does page 800 include all the modules loaded correctly when saved?
[*]The XPMM module from Angel provides the functions "YWALL" / "YRALL" to store everything into Flash 0x1FE and 0x1FF. While certainly not as easy to use as it requires Lib#4 and OSX and XPMM, I wanted to know if there are any other risks/objections to using this function?
[*]If these functions are not objectionable, would it be possible to add them to the YFNZ module so that one always has the ability to restore to a nice state from a ML condition and batteries out?

Thank you for your kind help!

I think that MEMORY LOST clears some 41C register information, but I've never
traced that sequence.

Saving page 804 will preserve the MMU programming.

Not all Flash devices have the segmented top block that make the YWALL easy to
use. If the top block is not segmented you'll end up erasing the entire block (pages
1F8 through 1FF). In addition, depending on the sequence, you may end up
inadvertently erasing 1FE when you attempt to write 1FF.

There is no room in YFNZ.
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12-31-2017, 03:37 AM
Post: #22
RE: Saving the state of HP41 CL to PC
(12-29-2017 06:11 PM)PeterP Wrote:  Waiting for @Monte to tell us about the V5 board behavior regarding sector 1F8 as per @Angel's comment. I was naively assuming upward compatibility (what works on V3 works on V5) which shows my ignorance when it comes to hardware. He probably also put it in the manual and I just cant find it / understand it...

The memory organization is explained in the Update Functions Manual. But
the top block is different with different Flash sizes. Plus, not all Flash devices
segment the top block. My original intent was to only use bottom-block
segmented devices, because that is where the OS resides, and would make
updating the OS a little more safe. But availability issues forced me to use
whatever was available when I had a batch fabricated. So some batches
had the bottom block segmented and some had the top block segmented.

So, to answer your question, on a V5 board the 1F8 segment is just another
block of Flash. I think that the best solution to this backup issue would be
to allow the functions specify which Flash pages to use, rather than picking
a specific page.
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