Calculator blog

Musings and comments about our common interest


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The HP16c mode

IMG_1048I am beginning to learn the HP16c through the HP16c mode in the latest HP15c CE. It is very expensive to get an original HP16c!

Unfortunately, the HP16c mode has a very nasty bug whereby the DEC screen mode does not represent well the X register's contents. The register contents are OK - it is the screen view that is wrong. It happens with some values only - but enough to be unuseful for real life use.

A member of the community developed a change in three positions of the original ROM. It is not that the original ROM was wrong - it was the emulator (which was designed for calculators that just use numbers in BCD) that could not manage some of the hexadecimal higher values. With reference to the original ROM memory space, the changes are the following:

06ef:000 (was:346)
06f0:000 (was:1cb)
0718:3ac (was:17a)
(addresses are the 10-bit word addresses expressed in the 16c ROM space - beware that you need to add the offset from the beggining of the firmware to the beginning of the HP16c ROM, and that the HP15c firmware is arranged in bytes, so that two bytes make a "nutbyte" of 10bits. You also need to consider that the memory is arranged "little endian".

We are now patching the HP15c CE calculators for the customers that ask for it. We are also offering the patching service for calculators in our customer's hands - in this case for a fee.

We will also receive soon a patching cable, valid for the HP15c CE, the latest HP12c (after 2015) and the HP10bII+ (anyone considering adding RPN to the HP10bII+ ?)

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Black Friday 2023

Now we have the Black Friday campaign at full speed. We have created a specific page with all the offers. you can find it here: Black Friday Offers

Among them you can find what is probably the most interesting item in our website (basically because we are the only ones that can offer it: the HP15c CE "Black Friday Edition", which includes:

  •  HP15c CE
  • Overlay HP16c 
  • Firmware patch to avoid the "DEC bug" that is only appearing in the NOMAS HP16c feature of the HP15c CE

For the Black Friday period, it is sold at the same price of the HP15c "nude": 107,43 € + VAT (none if you are from outside the EU) + shipping

HP15c CE Black Friday

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