HP 48SX invalid data message

[Giuseppe Donnini]

Exactly, that’s the classic approach.

Another technique, which usually requires less typing, consists in merging the port and then freeing it again:

n MERGE
{} n FREE

where n is the number of the port (1 or 2) in which you have put the card.

Here is some theoretical background information on this method by Bill Wickes himself:

(The following passage is quoted from his book HP 48 Insights - I. Principles and Programming, p. 105. A copy of the whole book is available on Eric Rechlin’s new webpage dedicated to HP literature.)

When you plug a memory card into either HP 48SX card slot and turn the calculator on, the calculator checks the card to determine whether the card memory contains a valid sequence of libraries and port variables. When the HP 48 cannot recognize the card contents, the message Invalid Card Data is displayed. If the card is ROM, the card is not usable in the HP 48, and should be removed. If the card contains RAM, you can ignore the message—the first attempt to merge the card memory or store a library or port variable there will organize its memory properly, and prevent further Invalid Card Data errors.

The PINIT command was added in the HP-48GX because one single card could now hold up to 32 ports, every single one of which must be separately initialized. Without PINIT, the annoying message would therefore persist until the user manually stores some random stuff in each port (note that my alternative technique wouldn’t work in this case, because a bankswitching card would only work in port 2, and port 2 cannot be merged on the GX). With PINIT this can be done in one go.