| SST change|
Message #35 Posted by Jake Schwartz on 16 July 2011, 1:44 p.m.,
in response to message #31 by Paul Dale
I can't win. I was given a hard time over the "dubious" SST behaviour of showing the step just executed.
First, let me say that you have been doing a fantastic job with this completely voluntary endeavor....your commitment to the project has been amazing.
Secondly, the SST function showing the step just executed in conjunction with the resulting X register shouldn't be considered "dubious", since that is how every HP RPN calculator works up to this point. Please hear me out as to why it should be this way.
First off, it has been made clear that the flash space is just about exhausted and adding things in at this point means possibly sacrificing existing things in return, which is probably a bad thing. The way it is now (with it showing the step not-yet-executed) has a serious problem when the step (call it step "n") just executed has been either GTO, XEQ or a test function (like "x=y?"). In these cases, the machine displays program step "n+1", which in the case of GTO or XEQ is the incorrect program step shown - it should be the destination label of the branch. In the case of a test instruction, the display always shows step n+1, which is only executed if the test evaluates to true. If the test fails, the step displayed is skipped.....again, very misleading. If it was returned back to the original way of displaying the step just executed, you would see the GTO, XEQ or test correctly, followed by the correct next step, whatever that is. I would bet that changing the logic with the existing situation so it showed the correct next step on GTO or XEQ would be fairly complex and would require eating up more precious flash space which isn't available. Plus, I don't think there is a logical solution at all for test instructions, in that the machine might not yet know what the next step will be, especially if the user moved the program counter (via GTO while out of program mode) to the test instruction and pressed the down-arrow in order to do an "SST" from there.
I hope this all makes sense and will justify returning to the "HP way".
Thanks for reading,