HP41 and EPROM

[Chris Gegg]

I am researching the development, functions, and capabilities of the HP41 (C, CV, and CX), but have been unable to find much information about the type of ROM and RAM used with the HP41. I have been through a large number of the HP41 manuals, but no luck. One main curiosity is whether EPROM was used with the HP41, either for the internal ROM modules or for the external applications ROM modules. Because the device was so versital, such as the magnetic card reader, I thought that it was likely EPROM was used with the HP41. I think I've seen a few references to ZEPROM-Modules and an HHP EPROM Box, but I haven't been able to find out any information about these devices. Does anyone have any information about these things or EPROM in general related to the HP41? Any documents or information would be great.
Thanks,
Chris

[Bill Wiese]

Chris,

Industry-standard 27Cxx EPROMs were only used on HP41s with various external 3rd-party boxes. These boxes had logic that adapted/translated between the standard A0...An, D0...D7, /CE and /OE lines of the parallel EPROM bus with the proprietary serial memory bus of the 41C.

HP ROMs (and HP RAM expansion "memory module" for the original 41C) used a proprietary clocked serial interface similar to prior HP calculators. These ROMs and RAMs were in 8-pin DIP packages. [However, do note that these are nothing like the current 8-pin industry-standard serial EEPROMs of the 93Cxx/24Cxx Microwire/I2C/SPI flavors.]

There should be details on this website and on "the other" 41 website how "Nut" and Classic HP CPUs communicate with HP serial memories.

Bill Wiese

San Jose CA