NoV-32: The New Hardware


PCB pannel

 

Latest NoV-32 and NoV-64 development required a double sided Printed Circuit Board with tracks and chips on both sides as well as metallised holes.

It is quite unlike one can build such a PCB by its own with simple hobbist tools and skills. Thus, it was necessary a completelly new CAD CAM design to meet the specs.

An European company offered a superb choice to produce relatively small amounts of panellised PCB's for a reasonable price.

The best part of it being that its manufacuring process offers an enviromental friendly silver platted finishing instead of the usual tinned one.

The final product, as shown in the picture, is of an oustanding professional quality.

The main IC footprint has been conceived to be fully compatible with previous Clonix-41 and NoVRAM designs so that all and every newly manufactured module will use this PCB, which is also ready to accept the four memory chips required for the future NoV-64.



Adapter PCB

 

Some of the modifications introduced at the very early stages of the Clonix-41 production affected the adapter board.

It beame evident that a DIL socket was neccesary to provide the appropriate rigidity and strength to that iterconnection part.

A standard high quality rounded pin socket was choosen for the task and solid phosphor-bronze gold-platted wire used to bond-weld the PCB to the socket. The result is a robust adapter built to last.

Some users have mailed me asking why the adapter PCB is not made from fiberglass board. Well it's intentional. Fiberglass board edges become very abbrassive, and this could wear the thin gold platted deposit in the module's connector. Chossing a soft PCB base material will protect the vaulable (in both senses) glod on the contacts.



 Top and bottom view of a NoV-32.

                                      


 

The NoV-32 (in the pictures besides) is a nice addition to anyone interested in the usage, experimenting, development, or just enjoying his/her HP-41 system.

For those concerned by the long term reliability of this new module (or the previous Clonix-41 and NoVRAM designs for that matter), mostly due to the usage of the 6.2v power supply directly from the HP-41 system, I'd recommend the reading of PIC18F252 Data-Sheet... ok, it's a huge document so just jump to page 259 "Absolute Maximum Ratings".

Although PIC18F252's max. operational supply is in the 5.5v, (and these limit are never surpassed while in operation) the manufacturer states that 7.5v is the upper limit above which the device may result permanentely damaged.

The power line circuitry has been calculated in such way that the HP-41 V+ line is dropped every time the module goes from Standby to Run mode. A simple resistor (with the unvaluable help of Ohms law) does the job. Thus module's operation remains below manufacturer's recommended working limit of 5.5 volts.

As for the Non-volatile RAM chips, they are powered from the PIC's port A lines, so they are out of the reach of the 6.2 volts from the HP-41 power line.