[HP4x] ROM Disassembly

[Han]

(03-11-2015 08:40 AM)Bruno Wrote:  [UPDATE 4]

I corrected the GX files.

I'm currently at around #22000h within the ROM and have verified the addresses up to this point. I also have a very different layout of library #F0h -- the command numbers on the HP48GX are no longer the same as those on the HP48SX. Libraries #A1h through #A6h are still the keys for each shift plane (no shift, alpha shift, left, right, alpha-left, alpha-right, though I don't remember if this is the correct order). It appears the matrix editor (#EAh) has moved into covered ROM. Library #A8h is where all the softkey definitions are, #A9h is where all the menus are defined (mostly arrays of pointers or romptrs in #A8h)

I'll post my .symbols.gx file and updated version of sadhp once I get a bit further down the entries list. (It will be for ROM R only). I think once we have fully labeled all the entries then we could probably work on fully commenting the ROM.

I had (a long time ago) thought about creating a custom ROM for the HP48G series (see this link) and even got as far as designs for reworking the card ports so that one could do direct execution from covered ROM. A custom ROM chip would not be hard to implement (I'd test on an HP48G and not GX first). I should be as "simple" as building a daughter card that is connected to the card connector, minus a few pins that can be wired to switch between the original ROM or the custom ROM (either the CE or NCE line on the ROM chip; I forget whether that chip uses inverted signals for its card enable pin).

Maybe once we get fully commented source, this can actually be realized. Too bad I have long since lost my earlier work with respect to the .symbols.gx file and have to start over, now.