I've just gotten the microcode of the HP-25 sort of limping along on an experimental version of my microcode simulator. This has been more challenging than my previous efforts because there is no publicly available documentation on the Woodstock instruction set other than an HP Journal article giving a brief overview of how it compares to the Classic architecture, and a snippet of the HP-25 ROM listing in a US patent. Neither source has sufficient details.
Most of the calculator functions do not yet work correctly. But the PRGM/RUN switch works, and SST and BST in program mode step throught the default "GTO 00" instructions correctly. Pressing the f or g shifts in program mode show the prefix keycode. But instructions can't actually be entered correctly.
R/S in RUN mode displays the correct step number and GTO 00 instruction when held down, and executes it when released. Other than that, in RUN mode almost nothing works correctly.
Low battery detect works, although since there's not much point to having low batteries in a simulator, I've now hard-coded the battery status to good.
In either mode, many operations cause a hang.
I suspect that there are fairly minor bugs in the simulation code that are causing these problems, but it may take some time to track them down. Once it is working, a new release of the simulator will be made available, although under a new name rather than CASMSIM.
A screenshot of two instances of the simulator running simultaneously, one in run mode and one in program mode showing step 01, may be seen here:
http://www.brouhaha.com/~eric/software/casmsim/experimental/hp25_screenshot.png
Warning, the image is about half a megabyte in size.