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HP42S with non-volatile ram
09-28-2020, 01:13 PM
Post: #6
RE: HP42S with non-volatile ram
Regarding pinouts, I couldn't find any official documentation about the pinouts of the processor used in the 42s, so I assigned the upper left corner as pin 1 when the logo in the TAB package was made to look upright. Besides, I couldn't find any other schematic of the 42s until I drew that partial schematic.
If you say "wrong", please show me the official documentation for the correct pin assignment.
If it found, I'll modify the schematic parts library to fix the processor pinouts in the schematic.

I'm sorry, I never thought that someone trying to modify a calculator wouldn't care about using such a thick board or insulation.

It seems easy to use the location of option ROMs, but at the point of poor power wiring for the parts at the time, there is a bit of anxiety about making strobe signals with the current high speed parts. So I implemented the logic IC in the part of the photo that seems to be better.
The series termination resistor of 100 Ohm for *CE is also inserted for that reason.
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Messages In This Thread
HP42S with non-volatile ram - GreyUser - 06-11-2020, 04:40 AM
RE: HP42S with non-volatile ram - mfleming - 06-11-2020, 02:26 PM
RE: HP42S with non-volatile ram - lyuka - 09-26-2020, 12:12 PM
RE: HP42S with non-volatile ram - GreyUser - 09-28-2020, 02:41 AM
RE: HP42S with non-volatile ram - lyuka - 09-28-2020 01:13 PM
RE: HP42S with non-volatile ram - GreyUser - 09-29-2020, 01:41 AM
RE: HP42S with non-volatile ram - lyuka - 09-29-2020, 09:48 AM
RE: HP42S with non-volatile ram - lyuka - 11-17-2020, 06:11 PM
RE: HP42S with non-volatile ram - G-SAN - 02-06-2024, 03:54 PM



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