Error in HP 48sx J rom ?

[Giuseppe Donnini]

The problem stems from the fact that the HP-48 ROM images officially released by HP are actually *not* pure ROM images, but ROM images overlaid with garbage originating from an MMIO chip. Because of this, all eleven official HP-48 ROM images produce invalid checksums.

We are all extremely grateful to HP for having released these ROMs, nevertheless, it remains a real shame that such a blunder could happen. The person who dumped these ROMs obviously had no clue about the memory chip configuration of the HP-48!

Thankfully, when a file is converted with CONVERT.EXE, the area between #00100h and #0013F is automatically zeroed out. However, if CONVERT.EXE is used as a mere checking tool (with no second argument), it does not complain upon encountering non-zero nibbles in the default MMIO chip area. I think it would be helpful if this behavior was changed.

On the other hand, ROM2EMU.EXE from the FILETOOL package, also by Christoph Gießelink, is a more general tool which is not specialized on HP-38 and HP-48 ROM images and, therefore, does not check nor alter anything during the conversion process.

So what happened is that you probably run CONVERT.EXE to create your revision E EMU image, but instead used ROM2EMU.EXE to create the corresponding revision J file.