41CL MMU Backup

[twoweims]

(05-30-2020 05:22 AM)Ángel Martin Wrote:  I hope I'm not confusing things, but If I understand the concept YFWR (1) temporarily remaps page #4 to 0x804, then (2) it runs the transient code, then (3) does the flash writing and then re-maps page #4 to its previous setting.

But this means than when using YFWR on 0x804 itself the information written to flash is under the conditions of step (2), so it says "page #4 is mapped to 0x804". Therefore restoring that block with YMCPY to 804 is going to preempt the actual page#4 mapping (in your case to the Library#4).

An interesting problem... maybe you can try to do a manual re-mapping to Library#4 after YFWR but you cannot perform any Library#4 dependent action until that is done, which it's unlikely unless the MMU is entirely disable of course.

"804>1F1"
YFWR - saves MMU settings with INCORRECT page#4

Then to restore things:

MMUDIS - disables MMU, so plain YFNZ is active
"1F1>804"
YMCPY - this step breaks the current Library#4 mapping
"804040-8120"
YPOKE - to restore that mapping
MMUEN - enables all mappings, so YFNX is active

I guess this means I should probably modify the YRALL routine in the PWRX module to include the fix, it was written with a previous version of YFWR (the one still included in YFNZ) that did not alter page#4 mapping in the saved flash block.

Ángel,
In the PowerCL Extreme manual, in the YWALL section, it says "Early CL beta user Geoff Quickfall prepared a few FOCAL programs to commit the calculator contents to FLASH, so that even without the batteries it’ll be preserved for a restore at any later time."

Watching Geoff's presentation from the 2011 HHC is what prompted me to start looking into this. Are his FOCAL programs available somewhere so I could study them to try to better understand this process?

Also, in your YWALL program listing in the PowerCL Manual, the comment next to YSERASE says "erase BLOCK" but YFERASE in the 41CL manual says that it erases an entire sector. Won't the second call to YFERASE erase the whole sector, wiping out the copy of 800 that was just put into 1FE?

I hope my questions are not too stupid. I am new to the 41CL and have been away from using my HP-41 in general for about 20 years. You can blame the Corona Virus for this. Staying at home prompted me to buy a second CL Board so now I am free to "play" without screwing up my daily use CL.