Some 30 years ago I wrote an mcode routine that changed the behaviour of the SST function (continuous SST); the routine wasn't implemented as a normal function, but directly integrated (hooked) into the operating system, replacing the normal SST function.
As I didn't program the HP 41 since these days, I forgot almost everything - and lost all my records.
The book "Mcode for Beginners" doesn't go deeper into these details. So I need help by mcode experts - please! ;-)

What would be the easiest way to realize such a function? Where can I find a book or an article that describes entry points to the OS in detail, and that provides a "how to do" description as well?
I am quite sure that such written information exists, otherwise I wouldn't have been able to realize my routine in the good old days.

Michael, here are two pointers for your search:-

First the VASM listings is a fundamental must, and the good news is that they're now available in a much better format than ever, thanks to Jackie Woldering's contribution in TOS (worth downloading).

Second, there's a pair of functions that may be doing exactly the same you describe, although not integrated in the OS. I included them in the TOOLBOX rom, took them from the NFC ROM so I assumed were written by Nelson F. Crowle. The functions are SST^ and BST^

Hope this helps, let me know if you can't get the references, I can email them to you.

Cheers,
ÁM.

Edited: 10 May 2013, 10:28 a.m.

Pst, it's save to link directly to the
VASM listing as it's not really part of TOS. And here's the same as
plain text.

Cheers

Thomas

I believe there was a CSST function published in some PPC calculator journal. That may be of some use. As mentioned before, the VASM listing is the way to figure it out.

I am also impressed that you implemented such routine as a keyboard extension, I did not think it was possible without resorting to page 4 programming.

The SST key works in different ways depending on whether the calculator is in program mode, in stopped run mode or stopped showing a catalog.

I improved catalog 1-6 about 30 years ago and I think that I added continuous SST at least to catalog 1 and possibly some others, but not all of them.

Thank you Angel, Thomas and Hakan for your hints!

I know that there are a few continuous SSTs around in several modules, but I am interested only in mechanisms of hooking the operating system. I hoped there were some more articles or example programs, but obviously that's not the case.
So I might have to choose the hard way, namely to take Raymond's advice and single step through the catalog extensions of the CCD module. It seems as if there is no better (closer) point for intercepting than the I/O interrupt.