A minor difference between the HP 15c CE and the original HP-15C (and LE)

[J-F Garnier]

[Referring to this thread, which I can't reply to]

On the new 15c CE, there is no noticeable display blink when you press a key such as x<>y or Rv, contrary to the original 15c or even the 15c LE (to a lesser extent).

Especially, when the x and y registers hold the same value, pressing x<>y or Rv has absolutely no visual effect, as if the key didn't actually act, and I feel this lack of visual feedback a little disturbing when used to the original 15C.

I'm not suggesting to modify this aspect in a future firmware update - I believe this has very little chance to happen - but I'm wondering if the beta tester team did consider this effect, or if it was considered as negligible.

J-F

[Werner]

Hi J-F,
I notice that my DM15L blinks at 12MHz, but not at 48Mhz.
That is to say, it doesn't blink for 'fast' operations like X<>Y, SQRT
But it does blink (@48Mhz) for eg 10^x if the argument is not an easy one.
1 10^x -> no blink
5 sqrt -> no blink but a subsequent 10^x does blink.
That would suggest that the blinking happens on a regular interval (independent of clock speed), and if the operation is too fast, it will be completed before the display can blink.
Since the CE is many times faster still, you probably won't see any blinking for any 'normal' function (not the solve and integrate).

Cheers, Werner

[brouhaha]

(11-06-2023 10:29 AM)Werner Wrote:  That would suggest that the blinking happens on a regular interval (independent of clock speed), and if the operation is too fast, it will be completed before the display can blink.
Since the CE is many times faster still, you probably won't see any blinking for any 'normal' function (not the solve and integrate).

That's exactly right. The blinking is done in the original Voyager hardware by the R2D2 chip, and is free-running. When the microcode sets blink mode, the display goes into whatever phase the hardware blink happens to be at. That is the source of most, if not all, of theRM-based 12C/15C LE/15C CE issues with display blinking, pause, SST, display of "running", error state, etc.

I have brought this up multiple times with HP, and recommended use of an independent hardware timer in the Atmel ARM chip to keep the blink state, withi an interrupt to the CPU enabled when microcode sets blink mode, but HP has consistently ignored me on this matter, and tried a bunch of other workarounds instead of fixing the root problem. Sigh.

[Valentin Albillo]

.
Hi, J-F,

J-F Garnier Wrote:On the new 15c CE, there is no noticeable display blink when you press a key such as x<>y or Rv, contrary to the original 15c or even the 15c LE (to a lesser extent).

Yes, I've noticed the same: when pressing some key which performs a fast functionality which leaves the display unchanged, it seems like nothing happened at all though the function was indeed performed. I also find this somewhat unsettling and wish some kind of feedback would happen on those cases.

Also, quite related, I posted this at the end of one of my recent HP-15C CE threads:

• Once R/S is pressed to start the timing of the matrix inversion routine, my CE immediately displays one or two running messages in very quick succession, then the display remains blank for the whole duration of the loops. This seems very similar to what happens with the dreaded LE's PSE (Pause) bug (except there's no PSE instruction whatsoever in my routines,) so perhaps the cause is somehow related.
  
  On the other hand, if timing the determinant routine, upon pressing R/S a single running message is immediately displayed once and it stands still, never blinking or blanking till the timing process ends. All in all, I find the display of the running message to be quite haphazard, sort of yet "unfinished business".

V.

[J-F Garnier]

(11-07-2023 02:26 AM)brouhaha Wrote:  

(11-06-2023 10:29 AM)Werner Wrote:  That would suggest that the blinking happens on a regular interval (independent of clock speed), and if the operation is too fast, it will be completed before the display can blink.
Since the CE is many times faster still, you probably won't see any blinking for any 'normal' function (not the solve and integrate).

That's exactly right. The blinking is done in the original Voyager hardware by the R2D2 chip, and is free-running. When the microcode sets blink mode, the display goes into whatever phase the hardware blink happens to be at.

The blink effect I was referring to is not related to the hardware blinking problem.
It's the short display off/display on sequence that happens when a key is pressed on the original 15C.
Very likely it is done with the DISOFF/DISTOG opcodes (although I didn't check).

This short blink is very visible on the original 15C, for every pressed key, including multiple key sequences such as "RCL . n" or "RCL DIM A", and was a convenient visual feedback.
On the 15c LE, the blink is much shorter due to the faster CPU but still noticeable, and on the 15c CE this blink effect completely disappeared. Maybe a side effect of some changes in the display management.

J-F

[Idnarn]

FWIW the blink on keypress occurs in the current gen HP 12C by Moravia (with the screwed door) which apparently shares the same hardware with the HP 15C CE. So perhaps it's more than just faster hardware that caused it to not occur on the HP 15C CE.