A ROM emulator for the 71B

[mfleming]

Hi Dave,

I wouldn't put this in the same class as a FRAM71, but let's compare specs.

The FRAM71 has 512 KB of non-volatile random-access memory which can be enumerated as ROM or RAM. It can serve up hard-configured ROM at E0000h and at 00000h as a system takeover ROM. It can cover the entire 20 bit address space of the Saturn CPU.

The - what shall I name it? - can enumerate 112 KB of ROM, including hard-configured ROM at E0000h and 00000h. It does not provide any RAM.

I assume the Diag ROM is a takeover ROM, so yes it could be emulated using the same shorting plug arrangement as the FRAM71.

The FRAM71 does require some mastery of the configuration process, but it is quite powerful. The whatever-you-call-it will likely be configured and updated the same way as a Clonix module. I'm consulting Diego on the best approach. The one I favor at the moment is a batch file or shell script driven by a simple text list of BIN files that will assemble the code and flash the processor. The programs needed to assemble and flash are available on Windows, Mac, and Linux so your development platform should be supported (MS-DOS on HP200LX excluded ).

If there's a particular feature you're interested in, let me know and I'll see if it is possible to implement. I'll rule out RAM right away, at least for this project.

~Mark