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HP-41CX w/ XF-Module - just curious
07-25-2019, 05:11 PM
Post: #8
RE: HP-41CX w/ XF-Module - just curious
(07-25-2019 04:16 PM)Sylvain Cote Wrote:  [snip]
Incorrect, the RAM part of the X-Function/Memory (inside the CX or in the plug-in module) is hardwired to memory address 0x040 to 0x0BF.
So when you plug a X-F/M module into a HP-41CX you create a bus contention because the internal module and the plug-in module actually fight to put their memory into the same address space.
I have tried it and observed that the internal module always wins, like I said before, I will have to check the electronic schematics to really know why that is the case.


When I inserted an XFM into a CX with multiple files stored, CAT-4 showed the first file (in the CX XMEM) and then jibberish characters, apparently confused by the bus contention Sylvain mentions. Though I wonder why the first file was intact. Upon removing the XFM module, the file chain in the CX XMEM was still intact, and I restored a file to verify the contents were also intact.

But I am curious why the CX's extra XFM ROM functions were not visible? If the internal ROM wins (due to lower page address) why would the extra CX XF Fns be hidden?

--Bob Prosperi
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RE: HP-41CX w/ XF-Module - just curious - rprosperi - 07-25-2019 05:11 PM

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