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HP-41CX w/ XF-Module - just curious
07-25-2019, 04:16 PM
Post: #7
RE: HP-41CX w/ XF-Module - just curious
(07-25-2019 12:44 PM)burkhard Wrote:  •The CX with no plug-in modules added has 124 Extended Memory registers.
Correct

(07-25-2019 12:44 PM)burkhard Wrote:  •There is an Extended Functions / Memory Module that is intended for the C and CV, not the CX.
Correct

(07-25-2019 12:44 PM)burkhard Wrote:  •This module supplies Extended functions + 124 Ext. Mem registers when added to the C & CV for which it is intended.
Correct

(07-25-2019 12:44 PM)burkhard Wrote:  •While a "naked" CX wouldn't need a second copy of the Extended functions, it *could* use more Extended Memory (it can hold 600 registers and only 124 are provided fromt he factory).
In a CX, you natively have 124 registers usable and you can insert 2 x Extended Memory module to bring it to 600 registers usable.
In a C or CV, you have to insert a X-F/M module first to get the first 124 registers usable and you can plug 2 x Extended Memory module to bring it to 600 registers usable.

(07-25-2019 12:44 PM)burkhard Wrote:  →So... Would the Extended Functions / Memory Module plugged into a CX add any Extended Memory? Would the user now have 248 (=2×124) extended registers?
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.

Sylvain
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RE: HP-41CX w/ XF-Module - just curious - Sylvain Cote - 07-25-2019 04:16 PM



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