HP-41 instruction print bug found

[hth]

(11-06-2019 04:14 PM)Monte Dalrymple Wrote:  

(11-05-2019 02:07 AM)hth Wrote:  Unrelated, but I am curious. Why is it that the 41CL cannot be unlocked easily using ENTER-ON or BACKARROW-ON, like the ordinary HP-41 can? I always have to pull the batteries to reset it when I made one of my many mistakes.

Simple answer is that MEMORY LOST does not disable the MMU, so if that is the source of the conflict it will still be present. If the machine is functional enough to respond to a BACKSPACE-ON it should also be functional enough to respond to a YRES command, which will disable the MMU.

Are you sure? I think the modified mainframe code disables the MMU on the cold start.

I am thinking of when you get the machine to lock up, pull the offending MLDL or HP-IL module and the only thing that seems to help to get control back is to briefly remove the batteries. The original HP-41 could usually be reset using ENTER-ON or BACKARROW-ON (without a memory lost if you press the ON key more than once while holding the other key). I think this causes the PC to be reset to zero somehow, but I have no idea how the hardware works. I believe very old HP-41s do not respond to ENTER-ON, my early 41CV did not when new. After I had the keyboard replaced by HP service a year or so down the road, it started to accept ENTER-ON. This particular unit is also the one I converted to 41CL a while back.