Saving contents of "extended memory"


Hi all,
Does anyone know of a way to save the contents of extended memory directly to the mag card reader/writer (without moving the contents into "normal" HP-41 registers)?


That's the only way i know of. They designed the card reader a couple of years before the 41cx so they probably never even thought of it. They started thinking ahead later and made it so you can write and read ascii and program files (but not what is really useful: data files) through the IL. So soon old - so late smart :-(


OK, this goes waaaay back in the past, when I was much more familiar with the HP-41 than I am now, so beware that this may be a shot in the dark!

The PPC ROM has a routine that allows the "curtain" separating the program from data to be moved, and I think that there was a way to move it sufficiently high to allow the extended memory to be viewed as normal memory (thus allowing routines in extended memory to be called directly). So I believe that there may be a way to use synthetic code to allow extended memory registers to appear as normal registers and then you can use the normal WDTAX card reader command to save the data onto cards.

After a (very) quick look at the PPC ROM manual, this is what I'd try

	XEQ "C?"	retrieve the existing value for the curtain
XEQ "CX" move curtain to nnn [1]
WDTAX save registers to card
XEQ "CX" restore curtain [2]

[1] do not ask me what nnn should be, I have no clue, perhaps somebody else will be able to help there.

[2] I assume that the curtain value we recalled on the stack in step 1 is now in the X-register. Make sure that this is really the case, or you may lose all memory.

NOTE: I think you do not need the PPC ROM for this to work, as the programs (C? and CX) are user code. If you are familiar with synthetic programming (see Bill Wilkes book in the MoHPC DVD ROM) then you can enter them yourself.



PS OK I found it!

Its in the PPC Calc Journal V9 N3, April 1982, "Extended Memory Topics", pp 21-27

Before you ask, yes, all PPC Calc Journals are scanned and available from
Jake Schwartz (member of the PPC ROM program committee) at


Edited: 29 July 2006, 3:20 p.m.

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