HP calcs with clock

[x34]

I wonder, which HP calculator models do have built-in RTCs?
AFAIK, these include HP-41, HP-71, HP-75, HP-48/49/50, 38/39/40, Prime.
And hi-end business models (which exactly?).

Also, I'm very confused with 28C/28S - all specs say it has no RTC, but there are lot of programs and docs using some king of internal timer. So, does 28 has any kind of internal clock/calendar ticking while calc is off? HP-42S?

tia
x34

[walter b]

Please don't forget the HP-55 and (in a way) the HP-45. Simply browse the museum you're in.

And the HP-20b and -30b also feature a RTC which allows the WP 34S to provide a stopwatch etc. Please see there.

d:-)

[Joe Horn]

(07-16-2014 07:31 AM)x34 Wrote:  I wonder, which HP calculator models do have built-in RTCs?
AFAIK, these include HP-41 ...

The 41C and 41CV have no built-in RTC, but one can easily be added to them by plugging in a Time Module. The 41CX has a Time Module built-in.

Some other HP calculators with built-in RTC include the 17B, 17BII, 18C, 27S, 94, and of course the 01.

[x34]

(07-16-2014 08:32 AM)walter b Wrote:  Please don't forget the HP-55 and (in a way) the HP-45. Simply browse the museum you're in.

And the HP-20b and -30b also feature a RTC which allows the WP 34S to provide a stopwatch etc. Please see there.

d:-)

Thanks Walter. I am not sure HP-55/45 clock keeps working while the calc is OFF.
So, could they be used as a pocket watch?

Sure, 20b/30b are in the list.

Joe, thanks! So, these are models, which could be used as pocket (or wrist) watch: 01,17B/17BII,18C,27S,41CX,20B/30B and 48/49/50,38/39/40,39gII/Prime.
And 71,75,94,95,100,200...

What about 28C/S and 42S? Do they keep counting in the OFF mode?

tia

[Les Bell]

(07-16-2014 07:31 AM)x34 Wrote:  And hi-end business models (which exactly?).

I couldn't name them all, but I do recall that the HP-18C (I bought my wife one, to replace her dead 33C) has a real-time clock with appointment scheduling and alarm features.

The 71B has a real-time clock but it's very limited by comparison with (e.g.) the capabilities of the 41CX or 41 Time Module. There are no alarms, for example, and it requires an (admittedly simple) program to continuously display the current time.

[Marcus von Cube]

(07-16-2014 09:56 AM)x34 Wrote:  

(07-16-2014 08:32 AM)walter b Wrote:  And the HP-20b and -30b also feature a RTC which allows the WP 34S to provide a stopwatch etc. Please see there.

...
Sure, 20b/30b are in the list.

To add some more info here:

The Atmel chip in the 20b/30b has a built in RTC but the stock firmware for the business calculators just don't use it because it needs the crystal oscillator to be reliable. (The same is true for all HP models using the same chip such as the recent 12C, 15C LE, 10bII+.) The RTC keeps the time as long as the processor is at least in one of the low power modes and not completly turned off.

The 34S stop watch is not based on the RTC circuit. It is just a piece of software that uses the periodic interrupt. It's only useful (and enabled) on a modified calculator as is the RTC.

[walter b]

(07-16-2014 10:34 AM)Marcus von Cube Wrote:  The 34S stop watch is not based on the RTC circuit. It is just a piece of software that uses the periodic interrupt. It's only useful (and enabled) on a modified calculator as is the RTC.

And a "modified calculator" is one with a quartz and capacitors added here. All that - as mentioned - can be read elsewhere (e.g. in the respective manual).

d:-)

[Katie Wasserman]

(07-16-2014 07:31 AM)x34 Wrote:  Also, I'm very confused with 28C/28S - all specs say it has no RTC, but there are lot of programs and docs using some king of internal timer. So, does 28 has any kind of internal clock/calendar ticking while calc is off?

The 28C/S has a built-in crystal controlled timer that runs continuously and can be read using a SYSEVAL call. However it does not have the firmware that converts this timer value into a date + HH MM SS, that's what those programs you found do. The built-in timer is 48 bits and clocks 8192Hz, so it's good for over 1000 years without rolling over. So yes, it does have an RTC, it's just one that reads (directly) in 1/8192's of a second.

[x34]

Thank you very much, Katie! So, 28C/S and 42S could be used as pocketwatches. Good! Will buy 28S, I love the form factor.

[rprosperi]

(07-16-2014 08:47 AM)Joe Horn Wrote:  Some other HP calculators with built-in RTC include the 17B, 17BII, 18C, 27S, 94, and of course the 01.

Don't forget the 19B and 19BII, younger bothers of the 18C

[Garth Wilson]

(07-16-2014 10:30 AM)Les Bell Wrote:  The 71B has a real-time clock but it's very limited by comparison with (e.g.) the capabilities of the 41CX or 41 Time Module. There are no alarms, for example, and it requires an (admittedly simple) program to continuously display the current time.

Most of the capability is there, but requires extra software to do it. It has ON TIMER# for example which can also wake the machine up when time to do something. There's CLOCKLEX (if I'm remembering the name correctly-- I merged a lot of my LEX files into one) which gives the a running time display in tiny characters in the LCD while you do other things, unlike the 41, using CLOCK ON. CLOCK OFF turns off the tiny running clock display.

[Christoph Giesselink]

Quote:What about 28C/S and 42S? Do they keep counting in the OFF mode?

In addition to Katie's reply some more information.

Yes, all three models (HP-28C, HP-28S and HP-42S) have a timer running with 8192Hz, even if the calculator is switched off. Because there's no possibilty to access this timer value on the HP42S only clock programs for the HP-28 are available.


Years ago I wrote two articles in the HP Articles Forum

275: HP28S: Hardware I/O basics
313: HP28C: Hardware I/O basics

and under section "Special considerations to master/slave operation" you can find some information about these timers.

The hardware timer is 32 bit wide and running @8192Hz, so the timer could hold values for (2^32)/8192Hz = 524288s = ~6d. That's of course too short for a clock with absolute time value. So the hardware timer is expanded by a 12 nibble (12*4 = 48bit) RAM area. To update the RAM content the interrupt capabilities of the timers are used. So the maximum timer time without an interrupt is reduced from 524288s to 524288s / 2 = 262144s = ~3d. So after maximum 3 days the CPU is awaked from sleep state (without turning display on) udpate the clock RAM, preset the timer for new interrupt and shutdown CPU again.

So only when you remove the batteries or put the calculator into "deep sleep" (aka. coma / storage) mode, the clock timer will stop. It's not recommended to put a HP-28 calculator into deep sleep mode, because of a hardware design bug the current drain is higher than in "off" mode.

At http://users.skynet.be/luc.pauwels/luc/H...clock.html is a clock program for the HP-28 series.

[Mark Hardman]

(07-16-2014 09:56 AM)x34 Wrote:  Joe, thanks! So, these are models, which could be used as pocket (or wrist) watch: 01,17B/17BII,18C,27S,41CX,20B/30B and 48/49/50,38/39/40,39gII/Prime.
And 71,75,94,95,100,200...

I don't see any clock/time/date functionality exposed on the 39gII.

The commands:

DISPTIME
5.152000 => DATE
10.1500 => TIME

Supported on the 38g, 39g and 40g do not work on the 39gII.

[Mark Hardman]

(07-16-2014 07:31 AM)x34 Wrote:  I wonder, which HP calculator models do have built-in RTCs?

Let's also not forget Katie's excellent hardware/software clock for the 97/97S.

Enhance your HP-97 -- Add a Clock and More

[Katie Wasserman]

(07-16-2014 05:50 PM)Mark Hardman Wrote:  

(07-16-2014 07:31 AM)x34 Wrote:  I wonder, which HP calculator models do have built-in RTCs?

Let's also not forget Katie's excellent hardware/software clock for the 97/97S.

Enhance your HP-97 -- Add a Clock and More

I guess it is "built-in" technically, but not natively.

Did you build this for your calculator?

Thanks for the reference!

[Mark Hardman]

(07-16-2014 06:19 PM)Katie Wasserman Wrote:  

(07-16-2014 05:50 PM)Mark Hardman Wrote:  Let's also not forget Katie's excellent hardware/software clock for the 97/97S.

Enhance your HP-97 -- Add a Clock and More

I guess it is "built-in" technically, but not natively.

Did you build this for your calculator?

Thanks for the reference!

Its on my project list.

I have one 97s with the BCD pod and one without. I plan on adding your clock (or something similar) to the latter.

[x34]

(07-16-2014 05:28 PM)Mark Hardman Wrote:  I don't see any clock/time/date functionality exposed on the 39gII.
Supported on the 38g, 39g and 40g do not work on the 39gII.

Yes, Mark, I do not see clock-related stuff in the manual.

Thanks, Christoph, now I am ready to get HP-28S in my hands.

Thank you Joe, I'll include 19 models in my search.

So, now the list of possible pocket watches comprises
01,17B/17BII,19B/19BII,18C,27S,41CX and 48/49/50,38/39/40,Prime
and models, which have RTC but it can be accessed only by changing firmware
20B/30B to 31S/34S, 15C-LE,12C-new editions, and I guess 39gII.