convert z80 rom to update file?

[critor]

Hi!



I've got a TI-73 rom dump, which I've extracted from the "ti73.clc" file that came with "TI-83+ Flash Debugger 1.0 build 20".

That rom dump includes os 1.50, and boot code 1.3005.


I've never managed to find the 73u update file for os 1.50 on the Internet.

So, I'd like to generate that file from the rom dump.


So is there a tool that can generate a correct unsigned 8Xu/73u from a rom dump?
If not, can you tell me how to do it manually, or how to program such a tool ?


Thank you very much.

[FloppusMaximus]

You may not be able to recreate the original OS update in the form that it would have been released by TI.

First, from what I remember, there's a bug in the TI-73 boot code - when an OS is installed, rather than saving the OS signature to Flash (as the TI-83 Plus boot code does), the public key is saved instead. (This also means that it would be rather difficult to write an OS that's capable of sending itself to another calculator.)

Second, TI-73 OS upgrade files generally contain two different headers - a "real" header at the start of the file, and a "fake" header on page 1A.

Third, if you got it from the Flash debugger, the OS was probably converted directly from a hex file, and not "installed" in the usual way.

All that said: it should be possible to create an OS upgrade file that would be functionally equivalent to the "real" one. You would need to extract the relevant pages, convert them into Intel Hex, add an OS header, and sign it somehow.

[brandonw]