HP250 curiosity

One thing I forgot to mention in my previous message is that a good book on this (and on programmign the HP41 in general, but not covering hardware or true machine code) is 'Extend Your HP41' by Wlodek Mier-J. I think yopu can still get new copies of it, if not, it's scanned on the MoBPC CD-ROM set. Other ways to get the synthetic instrucitons into the HP41 include using the barcode wand to read program barcode contianing the requeired instructions. The barcode loader deosn't cheack that the incoming bytes form a typable instruciton, it juect copies them into program memory. HP's book' Vreating your own HP41 Barcode' explains how to do it, it says certain combinations of bytes are not used, and those are the ones you want ! There were some 3rd party plug-in ROM modules (the one I have is called ZenROM) that let you driectly tpye the synthetic instructions on the HP41 keyboard. Somehow, that feels like cheating, though. -tony