HP 35s missing keystrokes

[Jeff O.]

(01-24-2015 07:14 AM)MarkHaysHarris777 Wrote:  Actually, most of those 'bugs' aren't bugs; ...I've found that 'most' of the bug-list is ... misunderstanding about either the nature of the 8502 processor and its interrupt mechanism...

Mark,
I assume the above statement refers to the lockup problem exhibited by the 35s, item no. 15 on the bug list. You have also mentioned "tight loops" in a couple of your posts, again, I believe related to the lockup problem. I certainly know nothing of the nature of the 8502 processor and its interrupt mechanism, but in case I misunderstand, I wanted to point out that it does not seem that the tightness of the loop has any bearing on whether or not the calculator locks up. Soon after the 35s came out, users reported instances of the screen going blank during program execution, with no response to any key presses. The situation could only be remedied by pressing the reset button, which erased all memory. The problem was ultimately found to be caused by using an equation as a prompt to stop the program and wait for you to press R/S to proceed, without following the equation immediately by a PSE or STOP instruction. Actually following with a PSE instruction only pauses briefly to display the equation message. If you want to display an equation as a prompt, stop the program and resume with R/S after keying in input, then you must follow the equation with a R/S. But then you must press R/S twice to get it going again. In any case, the “tightness” of the loop following the equation did not matter, it could be 10 lines or 1000 lines, but if it did not terminate naturally, it stayed in the loop, blank screen, uninterruptible. If a PSE was included after the equation to only pause briefly to display the message, or if the equation was followed by STOP with execution resumed by pressing R/S twice, the exact same loop could be interrupted by R/S or C, and the normal “running” message would be displayed during execution. Like I say, I know nothing about the 8502 processor and its interrupt mechanism (and I don’t really think I should have to in order to keep the calculator from locking up, should I?), but based on the only difference being inclusion or not inclusion of a PSE or STOP instruction, do you think this is really related to something as deep as 8502 interrupts?

(01-24-2015 07:14 AM)MarkHaysHarris777 Wrote:  I am planning to write a response (for new users to the 35s) to the bug-list on this site; not in an argumentative way of course, nor to generate any flame-bait comments... nor anything like that... just to give a more fair and balanced assessment of the HP35s as a professional tool for working engineers...

A fresh look by a new user such as yourself sounds like a good idea. I look forward to your review.

(01-24-2015 07:14 AM)MarkHaysHarris777 Wrote:  I'm really excited about the product, frankly. The more I use it the more I like it;

I can tell, nice to see such excitement about a product released almost 8 years ago. I agree that the 35s is quite useable and the “bugs” or quirks won’t impact most users most of the time. Its most unforgivable sin was that it was so close to being so much better, were it not for the bugs that seemingly could have or should have been caught before the design was almost literally carved in stone. (Carved in silicon, I guess.)