15c LE - PSE works and doesn't! Please explain!


Entering the PSE in a DSE loop yields the bug. The program from page 89 of the new handbook works just fine. Can someone explain?


That is probably because you don't execute another instruction between the consecutive pauses. If you try the example on pages 114-115, the display will only show the first result in the loop before ending the program. The bug will occur even if you don't use a DSE or ISG loop, for example 1 PSE 2 PSE 3 R/S will only display 1 and 3.

Edited: 28 Sept 2011, 3:04 p.m.


Unfortunately entering a second PSE in the page 114 progtam doesn't make it work. So there must be more to it than just two consecutive PSEs.
I have already tested some different cases that don't work. But why DOES it work in the cited case?

Edited: 28 Sept 2011, 3:08 p.m.


Because, like I said, you are not executing the pause more that once, you are just extending it. Try 1 PSE PSE 2 PSE 3 R/S. You will still get the first pause and see 1 followed by 3.


The bug problem is always present and apparent when two or more PSE commands are executed. It does not matter if the PSE commands are consecutive or separated by thousands of other executed instructions (i.e., a loop).

With 1 PSE PSE 2 PSE 3 R/S, the 15C-LE yields:

1 in display for one second (first PSE) (Everything is OK so far),

blank display for one second (second PSE) (BUG: 1 should still be in display),

blank display for one second (third PSE) (BUG: 2 should now be in display),

3 in display after program terminates.

Two consecutive PSE commands are two distinct executions of the PSE command. The second does not extend the first. The bug becomes apparent immediately with the execution of the second and subsequent PSE commands, until the program terminates.

Edited: 28 Sept 2011, 3:40 p.m.


The program on page 89 is very definitely not working as it should, i.e., as it would on an original HP-15C.

After entering 45 in Y and 50 in X, then executing f A, the value 38.2683 should be displayed for the length of two pauses (about two seconds), after which the program terminates shortly showing 39.2699.

Instead, the PSE bug in the 15C-LE causes the following: After executing f A, the value 38.2683 is displayed for the length of the first pause (about one second), then the display blanks for the length of the second pause (about one second), after which the program terminates showing 39.2699. Bad!

This PSE bug that I reported here on September 10 only becomes apparent after more than one PSE is encountered in the program runstream, as it is in this program. The first PSE works OK, but subsequent PSE commands disrupt the LCD. It is immaterial whether the PSE commands are in any sort of loop, DSE or otherwise.


Ah, I didn't realize the 2-PSE-requirement for the bug to appear. Thanks for clarifying.

Edited: 28 Sept 2011, 3:39 p.m.

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