Hp-41 time module options


My HP-41CX has been upgraded with an HP-41CL board, which is absolutely great - the combination of ~50x speed and (for all practical purposes) unlimited flash and RAM is a real vitamin injection :-)

The only problem is that the 41CL does not have anything equivalent to the time module - it has the code, but not the actual timer chip. The obvious solution to this would be to add a time module, but these appear to be scarce. I have the timer chip on the old CPU board from my HP-41CX, but I'd rather keep that intact.

I'm wondering if it might be possible to program the Clonix-41 to emulate the timer chip. If so, then that might be a solution for those of us that have a Clonix (or one of the later designs). Alternatively, it might be possible to use a chip from the TI MSP430 series - these seem quite cheap (you can get development kits for $4.30!), and have been used in watches, so one might assume that they have low power requirements and a means of keeping track of the time.

Any thoughts on this?


Please see this post...

Geoff Quickfall - Physical Ports

Edited: 5 Dec 2011, 3:26 p.m.


I´m hoping Diego reads this and shares his thoughts on this intriguing idea, which I agree would be cool.

Another thing could be using the real Time Module (assuming you've got one) as physical frame for the serial connector, so as to kill two stones with the same bird (sic.) - but I guess there isn't enough room inside for such a hack.

Edited: 5 Dec 2011, 4:57 p.m.


Got to agree, if someone could come up with a time module crystal assembly which can be plugged into a donor ROM module, Fantastic.

Time modules are rare so far.

Don't see the need to free up physical ports though, other then finesse. For example, I am using the:

-IR ROM, which is swap when using HPIL to avoid printer/HPIL conflicts
-time module
-serial port connector.
-on occasion I will insert the CLONIX when updating the CLUTILS,
other ROMS not built in or YFNS.

So I have always got one free port or two if I remove the IR module. As far as other modules, my automated UPLUG/PLUG routines with various subroutines will add any number or combo of the built in ROMS.

Cheers, Geoff


How does the time signal send to the main HP-41 board over the flex PCB, is it digital or analog.

Since serial ports on the 41CL remains attached and If the clock signal is an analog signal, perhaps a time module circuit (Crystal, IC, cap, etc) could fit into the 41CL serial port cover, power from the flex PCB (battery) and send clock the signals via some wire either to the flex PCB or directly to the 41CL core.


It is digital, using the normal HP-41 serial bus signals.


I´m hoping Diego reads this and shares his thoughts on this intriguing idea, which I agree would be cool.
This is something I've already thought about: adding a RTC clock such as the
DS1340 into a Clonix module to provide an HP Time Module emulation, but I've not checked in details the specs of both the Time module chip and the RTC to see what would be the effort required to emulate the first one.

The serial connector that comes with the 41CL board does not fit into an empty module housing. There might be another place for a serial interface as indicated on the picture below but you would need a connector similar to the ones used in 48 models, and this solution might have other drawbacks ...


And as you can see here, you can even have a built-in time module:


Thanks for sharing, very nicely made! Do you have the schematics on this time module and how it is connected to the HP-41?
Regards, Kerem


Unfortunately, that is a TIME MODULE ROM chip, just moved inside to free up a port.

As stated, it is not the physical ports that require freeing as 99% of the ROM modules for the 41C reside in the CL. It is the rarity of a TIME ROM module itself.

The question is, can one be made from scratch and added to the board. With a spare TIME MODULE as an example, I don't see why a time module kluge would not work and attached as in Juergens picture. Just costing it with the limited production run of CLs might preclude its production unless someone comes up with a DIY kit.



How is the time module built into a 41CX? Is it a separate module or is it a part of a larger sub-board that includes Extended functions and memory?



The time module chip is included on the HP-41CX CPU board.


Unfortunately, that is a TIME MODULE ROM chip, just moved inside to free up a port.

Exactly. Of course it would be nice to have a replacement solution but I fear there are not enough interested parties to bring back the development cost so it's even harder to find someone who jumps in this project.

It is the rarity of a TIME ROM module itself.

Well, it's not that rare but prices definitely have raised in the last months.


I always wanted to include the timer function, but it just

isn't practical using programmable logic.

Just the registers in the timer chip require 382 flip-flops,

which immediately dictates the use of the largest available

Xilinx Coolrunner-II CPLD, which is a $40 device. To make

matters worse, that part is most readily available in a 208

PQFP package, which won't even fit on the 41CL circuit board.

The other available packages are all chip-scale, which means

higher assembly costs. These package options also have minimum

order quantities of several hundred.

I am about half done with the reverse-engineering of the chip

in case things change in the future.


Would a fleapower microcontroller be able to do it? I'm envisioning a crystal oscillator with CMOS logic to divide it down, to interrupt the microcontroller 100 times per second and wake it up for just a few instructions' time to update the registers, see if they match the next alarm time, etc., then go back to sleep. The microcontroller's own clock would be RC type so it doesn't take a lot of cycles to stabilize and be ready to run, assuming it needs to run faster than the time reference crystal when the calculator is talking to it. If the calculator is turned on, then the microcontroller would probably have to be alert enough to perk up its ears when the calculator talks to it.


Should be able to do it. Keeping the time is only a small part

of what is required though. The bigger task is interfacing to

the 41C bus, accepting commands, etc. in a compatible fashion.

Perhaps some combination of a small cpld to do the interface

stuff and a uC to do the timekeeping/registers would be the

best option.

Edited: 8 Dec 2011, 1:25 p.m. after one or more responses were posted


This is the reason I mentioned Clonix as a possible host for this functionality - it already has the code for communicating on the bus, and the processor used appears to have timer/counters that could be used to keep track of time.


Hi all,

And again sorry to join this thread so late.

Most of Monte's reasons to discard TIME module into CL logic are applicable for the Clonix approach.

TIME module is *not* a simple ROM pac but a very complex peripheral device wich has a whole set of dedicated commands and can both "request" CPU attention and make its own "decisions" according to events requirements like alarms.

Current Clonix family only handles a few "commands" (or pseudo commands) that is some codes that 41CPU cosiders as NOP's.

Only exception is the emulation of the double X-MEM memory for the Clonix-D or NoV-64 which decodes a few "real" intructions.

All of the above does not means that the project itself is not appealing... on the contrary, it certainly is!! :-)

However, it may well be a little too much for the limited processing abilities of the microcontrollers used into Clonix or NoV; and one thing is for sure: HW desing *must* be very different.

So, the other point would be: are not enough TIME modules out there to fulfill the HP-41CL's users needs?



Ok, I guess that's the definitive answer as regards the suitability of the Clonix for this purpose :-)

I don't know if there's actually a lack of time modules in the marketplace - all I know is that I don't often see them available on eBay, and in general, they seem to be priced quite high (compared to, for example, a complete Hp-41CX, or a 41CL board).


Pitching in very late here - but I believe I have a couple of spare Time modules if anyone are interested. I am not interested in money in return, but rather some HP calc stuff.

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