The first step in emulation of a TI calculator is obtaining an emulator. This is a program that interprets Z80 instructions and runs them on your PC. Basically, it fools the calculator programs into running on a foreign architecture.
There are a number of emulators out there, but the best one I've found is Virtual TI. It can emulate any (?) graphing TI calculator, provided that you give it the proper ROM (see next section). It even has skins, so it looks/feels like you're actually using the calculator. Or, you can create your own skin, and change the layout of things to something better. I have on-site Virtual TI v2.5 Beta 5, which is for Windows.
Once you have an emulator downloaded and installed, you're ready for the next part...
A Z80 processor alone does not a TI-85 make. Coupled with it is a ROM BIOS, which contains the so-called TI-OS, and controls program execution, I/O, etc. This also contains the majority of the mathematical functions, since the Z80 has extremely limited mathematical capabilities. So, in essence, the ROM dump is taking all of the software from the calculator that makes it a calculator.
The only legal way to obtain a ROM dump is to purchase a TI calculator and a Graph-Link, and use special software to perform the dump. (Note: VTI can do ROM dumps for most calculators) You may only legally use/possess a ROM image that you dumped yourself from a calculator that you own. If you do not own the calculator from which the dump came, you are infringing on copyrights held by Texas Instruments Corp.
Of course, there are sometimes circumstances that prevent you from legally obtaining a ROM dump: perhaps you don't have a Graph-Link, or your calculator was damaged and no longer functions. You should still have the right to get the ROM image by other means, right? No, you absolutely must create the dump yourself, otherwise you're breaking the law. That said, I have available for download several different ROM dumps.
Whether you own these calculators or not, you are not legally allowed to possess these files, so download at your own risk!
I put these dumps at your disposal because I realise that you might not want to spend $150 on something that you're just going to play around with and possibly never physically use. I'm only using them as an interface to a Z80 processor, to familiarize myself with embedded software design. Someday I might actually buy one or more of these calculators, but for now I'll just use my illegally obtained ROM dumps.
Also, you'll notice that there is a version number next to each ROM. Could it be that Texas Instruments actually releases different versions of the same calculator? Yes, they do. This is because they fix bugs, add functionality (minor), etc. There are obviously a lot of different versions of some of these. I believe they're even starting to offer flash upgrades for the newer models. You can find out what version ROM you have on your calculator by entering the following key sequence: (This will actually try to self test, but it displays the ROM version at the prompt)
[2nd] [Mode] [Alpha] [S]
WARNING: If you do this, do not press Enter! Doing so will reset your calculators memory. Just press any other key when it asks "Enter self test?" to exit without erasing all your data.
Once you have a ROM, give it to your emulator and start it up. Now you should have a fully function TI-8x on your computer!
Please feel free to send me any questions/comments/links/etc you may have. I'll try to respond to everyone's email A.S.A.P., but occasionally I get really busy.
email: ticalc_z80@yahoo.com
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