HP41 key press delay (for NULL)



#2

On the HP41 if you hold down a key you will see the function that is assigned to it. If you keep holding it, the key press is cancelled and you see NULL on the display. This is very useful if you want to see which function is assigned to a key (in USER mode) or which program instruction will be executed by SST, etc.

Unfortunately the timeout value is a constant hardwired into the HP41 firmware. It is just a number, independent of the CPU speed.

So under certain HP41 emulators this timeout is extremely painful, as you have to press and release the keys very fast to avoid cancelling their action.

While looking around the HP41 sources I have found the relevant bit of code.

The VASM listing is on the MoHPC CDROM, file 41VASM.pdf, page 113 (in the PDF), 112 in the document.

The line is

1306   460   LDI
1307 1100 CON 576 INITIALIZE NULL TIMER

The timeout is 576 (decimal), or 1100 (octal), or 240 (hex).

So how does this help?

I have looked at the binary ROM dumps and I have found out that the timeout value is in ROM 0, offset 1D8E.

This offset is the same on the F, G, and N ROMs.

**vp


#3

I've suffered this very problem you mention and it is **incredibly**
annoying !

Is there any short routine or 'patch' that would deactivate
and/or increase this value in the V41 emulator, so that
the problem would dissappear altogether ?

BTW, the HP-15C also has this NULL feature for some of its matrix functionality: when you press STO B/RCL B, say, the (i,j) indexes of the stored/recalled element are displayed briefly while you hold the 'B' key pressed. If you then release it within a certain lapse, the STO/RCL is performed. Else, NULL appears on the display and no action takes place, exactly like in the HP-41C. This is extremely useful when accessing a number of matrix elements if you forget what element is the current one. I thought I would mention this, as a further example of the vast amount of attention-to-detail used in the design of the HP-15C. Those were the days ...

Best regards from V.


Possibly Related Threads...
Thread Author Replies Views Last Post
  This is not the yellow press ... Walter B 101 6,734 12-17-2012, 10:19 AM
Last Post: Maximilian Hohmann
  Apologies on mail delay. Diego Diaz 0 364 11-07-2012, 02:27 PM
Last Post: Diego Diaz
  HP news in the press Randy 1 512 05-08-2012, 09:18 AM
Last Post: Walter B
  Updated: Some press articles about the new 30th anniversary 12c Gene Wright 13 1,595 09-01-2011, 08:57 PM
Last Post: gene wright
  HP Press Release about the 30th Anniversary 12c and 15c LE Gene Wright 27 2,999 09-01-2011, 07:18 PM
Last Post: Glenn Dowdy
  HP 41CX NULL MESSAGE Derek G. Graham 1 409 01-01-2008, 04:30 PM
Last Post: Karl Schneider
  TI 17bii solver: after you press the CALC key Don Shepherd 1 415 11-10-2007, 01:41 PM
Last Post: Bill (Smithville, NJ)
  HP35s in the Press (Spectrum Magazine Oct 2007) Chris McCormack 5 749 10-13-2007, 01:54 AM
Last Post: brian healy
  HP 35s Press release Howard Owen 0 339 07-13-2007, 06:29 AM
Last Post: Howard Owen
  33S key press problem kc 10 1,135 02-05-2007, 12:42 AM
Last Post: Forrest Switzer

Forum Jump: