now, how is that even possible? The backup battery is now internal. I tested it /several/ times, opening/closing the case, swapping main power-sources...
Today I loaded up ZAC and ASMIDE again, popped open the case, and it was wiped again!
So I tried several times to repeat the wipe through the actions I'd taken earlier... and... nada. Thing holds its memory fine despite everything I threw at it. Pulling the batteries when it was on, pushing "On" when the capacitor was discharging, plugging in the external battery pack, unplugging it, opening and closing the case... nada. Memory Not Cleared.
Frustrated with that one time of unrepeatable flakiness, I decided to just logic-probe-around anyhow, get the jist of what it does when it's empty and sitting at the blank prompt.
Yeah. I crashed the thing hard, several times, shorting pins while probing. And I was being quite careful.
This is no easy task, working on this thing's hardware!
Again I'm half-tempted to just assume I'm right about being able to piggyback my FLASH chip atop the ROM, and a tiny bit of Glue-logic to map it in the 128k above the RAM... but... that just doesn't seem very scientific-methodological to me. And, besides, I was kinda hoping to map it elsewhere, which would require a different glue-configuration, and less-likely unused pin functionality that should probably be tested first. I dunno.
"Memory Cleared" is a pain!
WHat On Earth?!
Now it's starting up saying "Memory Recovered"?!
Days, and MANY uses later: Found this: https://www.ticalc.org/cgi-bin/zipview?86/asm/programs/zac.zip;Zac.txt
Nice One, ZAC... saved the day many times over.
Crash protection ---------------- When a compiled program is run with the "[ENTER]=Run" command, crash protection is installed before execution. It is a very limited anti-crash, and it will not work if it's a serious crash. If you see that your prog is crashing, or behave strangely, press ON, and you'll return to the homescreen (hopefully...). If your program is really buggy and the calc crashes, remove one battery, and put it back. Then turn the calculator on, as if nothing has happened. If you see the "Memory recovered" message, then you didn't lose anything :) WARNING: It doesn't work every time. Be sure to backup any important files before trying a program.