MLDL2000 now working as MLDL!


Good news today! I just got the MLDL really working with MLDL capabilities. The WROM instruction is now correctly recognized. There was a very nasty little bug outside my state machine, and it turned out that the WROM instruction has been working all the time. Just reading the data back from MLDL SRAM failed.

For those interested: The MLDL I now created has one 4K page of SRAM at $E000. I have used an Eramco ROMBOX with several Eproms to test writing and reading individual words in the SRAM with the DAVID ASSEMBLER. Second test was to copy the ERAMCO ESMLDL-OS Eprom contents into page $E000 with the COPYROM instruction that is in ESMLDL-OS. Unplugging the ROMBOX left my good old HP41C (2* speedup) with only the RAM connected, and CAT 2 showed the copied ESMLDL-OS! My other machine, a non-speeded HP41CX, showed the same behaviour.

I will put some pictures I have just taken of the prototype on my website, but that could take a few days. Will let you all know when they are online.

Next step is to test the prototype with FLASH and multiple RAM pages. This requires to load larger amounts of data into memory, and I need the external I/O interface for that. The hardware is pretty simple but I need to do some software programming on the PC to be able to bit-bang the control signals of the external interface of the MLDL.



Feliciteerd Meindert, dat gaat wel heel snel zo! Nederland wordt HP 41 land als je zo blijft doorgaan!

Congratulations Meindert, that's going really fast! Keep it up and you'll make Holland HP 41 country!


Congratulations, Meindert!
Will be certainly interested in getting one or two of your MLDLs.
Thanks in the name of our community


Meindert, congratulations for your success! I'm highly impressed by your achievement in your spare time. Many other projects, especially difficult or timeconsuming ones are never finished. I'm very positive to be able to buy an MLDL in the near future.
Best Regards


Dear Meindert,

also from my part I want to send you my congratulations!
It is incredible how your project is proceeding. HP41 seems to experience a sort of Come-Back these days due to great efforts of people who deliver a lot of HP-material, great programmers creating new emulators (e.g. Jean-Francois, Warren, HrastProgrammer, and many other very good emulator programmers), and hardware experts like, e.g., Christoph Klug with his IL interfacing solutions and last not least you with your MLDL ! And of course there are many other good guys I did not mention here (sorry!).

All in all - even without HP - within internet age the great HP41/HPIL system concept is again very much alive, I am happy for that as I grew up with this marvellous machine.

Today it still seems to be easy to get a HP41CX (e.g. at Ebay) but it is NOT easy to get RAM that allows MCODING and loading available ROM-images. And that is one of the main "add-on"s which we 41-enthusiasts all need very urgently!

Meindert, I would be happy if you please could take me onto your list, I would like to get one of your fine MLDL when it is finished! (but please take all the time you need as it is certainly a lot of hard work).

Best regards - and "happy programming",


(Werner Weiershausen from Darmstadt/Germany)


For those humble ignorant like me :
What is MLDL ?

All the best



Machine Language Development (Laboratory?)

It is a device with RAM where HP41C ROM's are addressed, and with a means to write information into the RAM. With it, you can write your own HP41C machine language programs or load images of existing ROMs.


That's great news Meindert!

Thanks a lot for your efforts and willingness to share them with us.

I wish it's already Xmas... ;-)


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