HP48GX RAM card design

[Eric Rechlin]

(01-18-2021 03:51 AM)wan Wrote:  I made a piece, but there are some modifications:
gold fingers flip to the back;
add rounded around the card;
1.6mm is too thick, use 0.6mm board instead；
eliminate all the pull-up resistors of we and oe lines.
no bank swiching.

it works well so far.

In his Readme he wrote that 1.2 mm was too thin and to use 1.6 mm instead. How does 0.6 mm work then? Wouldn't that be way too thin for the connector?

The connector on the edge of my RAM cards is actually 2.0 mm thick, with the total card thickness being about 2.5 mm, so I would think a better approach would be to start with something approximately like what you did (a 0.6 mm board with the gold fingers flipped to the other side), and then add a second bare 1.2 mm board glued to the top, with holes for the components to go through it, to add thickness (for the edge connector) and provide some protection for the components on the board.

Also, what was the reason for removing the pull-up resistors on WE and OE?

Finally, might you be able to please share your modified layout?