HP42S with non-volatile ram

[GreyUser]

As is typical for HP pc board layouts, all chips have their pin 1 facing in the same orientation.

The cpu pin 1 indicator is obvious with the protective plastic frame removed from the tab package. With the frame in place, it is approximately 50% covered. It is the round, hollow circle in tinned copper on the kapton film of the chip carrier, in the lower right hand corner. It is above pin 14 of the ram chip, partiality obscured by the protection frame. Above 1/2 of the diameter can been seen with the plastic frame in place.

I have completed a pinout of the LCD, only hand drawn at this time. I would be happy to share with you if wanted, send me a PM. I intend to make a formal drawing and add it to the archives here on the museum when time permits. I am the author of the Pioneer keyboard schematic that you referenced that is in the archives here.

Thank you for sharing all your excellent work with the 42S!