The Systemyde 41CL takes advantage of modern technology to significantly
add to the capabilities of the Hewlett-Packard 41C system. The 41CL circuit board replaces the original CPU board in the calculator and
provides all the features of an HP-41CX except for the Time Module. CX Time functions (the software) are included, but
a Time module plugged into a Port is required for full timer functionality.
The full 600-register Extended Memory and over 290 plug-in module images are built in. Functions are included
to allow these images to be virtually plugged into a calculator Port and unplugged from a calculator Port, either from
the keyboard or from within a program.
A Turbo mode is included that allows the calculator to run at up to 50X normal speed.
A total of 512 pages (4K in length) of Flash memory are available for non-volatile storage. Roughly 480 of these
pages are pre-loaded with 41C software. A total of 128 pages of RAM are available. Seven of these pages are pre-allocated
for 41C use, for register memory, extended memory, MMU contents, and 41CL buffers. A sophisticated Memory Management
Unit (MMU) allows full access to the large physical memory.
Full bus compatibility for the Ports is preserved, allowing the use of any peripheral designed for the HP-41 system.
Updated image: FLDB_V2 because of three typos (thank you, Sylvain). Also, slightly
modified the format of mem_ref.txt and mem_ref_v2.txt to make it easier to parse.
Updated image: Z4DL.
Updated image: Z4DL.
Updated images: 3SWP, ISOL, SIHP.
Fixed a typo in the FLDB.
Updated images: ETS3, UNIT
Updated images: ETS3, ETS4,
Updated images: ETS3, ETS4,
ETS9, FFEE, FUNS
Updated images: ETS4, ETS5, ETS9, H67G
Updated images: ETS4, ETS5, ETS9, SM44
New image: H67G
Updated images: ETS5, STEQ
Updated images: TEST, ETS4
New images: PPC9
Updated images: TEST, ETS4
New images: E-6A, KRMK
Updated images: CIVI, MENG, PHYH
Deleted obsolete images: 4AOS, 4PLY, 4MTR
Updated image: HEP2
Since space in the Flash is getting tight, I'm leaning towards removing YFNS and YFNP. Since
YFNS merely changes the XROM number of YFNZ, you can just copy YFNZ to RAM and change the XROM to whatever
you like anyway. YFNP replaces some of the FAT entries in YFNZ with IMDB stuff and the YCRC function.
All of that stuff is available in YFNX. I might also modify YFNZ to add the YCRC function and a function
to check the Flash size, in place of the YBPNT and YBUILD functions, which I don't think anyone has ever used (and
they're in YFNX anyway.) Anyone reading this feel free to send me feedback either way.
Updated image: XPMM
Updated images: 4LIB, TTRC, XPMM
The FLDB has also been updated, because of these updates. I'll get to FLDB_V2 at some point.
Updated FLDB so that blank and empty pages have the correct CRC value. Created one
.zip file with all the images to simplify updating a 41CL.
Updated image: TTRC
Updated image: TTRC
Updated image: TTRC
Updated images: 4LIB, ROMX, XPMM
New image: 4WIN
The FLDB has not been updated yet, because I know a change to TTRC is coming, and I'll just have to update it again.
Fixed dyslexic file name: GRF1
Updated images: XPMM, GRF1
Updated image: YRGA
Deleted obsolete image: CLUT
New image: YRGA
Updated image: XPMM
Notified of errors in the flash database (thank you, Sylvain): FLDB
Updated image: GJMR
Updated again: PWRX
Updated image: PWRX
Three updated images: OSX3, ROMX, XPMM
Two new images: CAB4, GEOD
Three updated images: NONL, XPMM, YFNF
Boards are back from assembly, with piezo attached, CPLD and FPGA programmed. Just
need to update the Flash (45 minutes per board, ugh.)
Five new images: ROMX, GRF1, GRF3, GASL, GASU
Modified the "Updating the 41CL Flash" document.
One new image: HNDY
One updated image: XPMM
Parts and bare boards shipped to assembly house today.
One new image: ADVG
Two updated images (SERI and 4RAM). Preparing to order another batch of boards.
One new image: 141B
One new image (GAMX) and one revised image (FUNS).
Two new images (DBUG and RCRD). RCRD is the Card reader ROM, which I had not previously included because it is hardware-specific.
But Gene Wright pointed out that there are some routines in the image which might be useful without the card reader actually being
Several new images (AGAM, GRMK, RGME, SR1B). Several modified images (ADV1, ADV2, 2SWP, GSB2).
A couple of images went from 4k to 8k, so they had to be moved (GSWP, MAHJ, BASI). One image
obsoleted (GTWN). Refer to the Memory Reference for details.
New image: Outer Planets (OPLN). The holes in the Memory Reference are where
I finally deleted the obsolete images to make room for new stuff. References to those images
were removed from the IMDB a while ago, so nobody should still be using them.
A few revised images, and several new images.
New image: Games Solution Book 1/2 (GSB2). Removed obsolete image references from IMDB.
New image: HEPAX Periodic Table (HTAB). Also, discovered that I managed to lose the image
for the WPN Effect ROM. Incredible.
New version of 41Z Deluxe.
New version of 41Z Deluxe. Added link for Michael Fehlhammer's awesome overlays.
All of the current batch are spoken for. I still have
one V3 board and two V2 boards available. You can still submit an order for a V4
board, but I don't have a schedule for when more boards will be available.
New version of 41Z Deluxe.
New mnemonic (Z4DL) and version of 41Z Deluxe.
New versions of several images, and a couple of new images.
Updated versions of SM44 image and documentation.
Remember the CL that wouldn't work after the PC it was connected to went to sleep? The one where
the CL board worked in a different calculator body? It's been sitting on my desk, assembled, for a week.
On a whim I inserted the batteries and turned it on and presto - "MEMORY LOST." Incredible. It had to
have been some wierd state being retained in the display driver chips, or some kind of memory
mechanism with the batteries.
Added updated Sandmath 4x4, plus two new images.
Updates for revised Library-4. I still haven't figured out what happened when the PC went to sleep with a 41CL connected.
The board works fine in a different calculator body. Grr... makes no sense.
Two modified images. Fixed a typo in IMDB (thanks, 'Angel.) Making serial connectors today.
Revised the Updating the 41CL Flash document. It turns out that you need to
be careful with the serial port. My PC went to sleep while I had the serial port connected, and now the 41CL
doesn't work! The only thing I can think of is that a voltage transient somehow made it to the CPLD.
Revised the Updating the 41CL Flash document. Updated
the 41CL Memory Functions to -1D to fix a problem displaying the address and data with YPOKE+
and YPEEK+ functions. The functions worked properly, but the display of the result was
messed up for one character.
Revised the Updating the 41CL Flash document. There is
a problem with the method used to determine if you have one of the early V3 boards. It looks
like the YPOKE with a Flash destination isn't working for some reason. I'll post an update
when I figure out the problem.
Updated the 41CL Dynamic Library to -3A to add more options for the PPLUG function
when using a direct page address. If you never do this, the update is not necessary.
Updated the "Other Docs" page with more documentation.
More new images.
Added some new images. Tweaks to various documentation. Also, check out my article comparing FPGA technologies in the
December Circuit Cellar magazine.
Released the Updating the 41CL Flash document. Feedback welcome.
More new images added to the memory map.
Added a few new images to the memory map. Working on a "Flash Updating for Dummies" paper.
Noticed something I don't like about the "PLUG? ?IMG ?" function with the V2 version of the
Image Database, which has a bunch of NULLed entries. Pondering whether or not it's worth fixing.
Finally took the time to try serial port downloads to the 41CL. Works fine using CLWriter.
Even managed to update the OS sector on a customer machine without bricking the machine!
Used serial CL-to-CL transfers to update my machines. Managed to mess up twice. The first time I
was using YFNX on the target machine and erased the sector containing YFNX.
Dumb. Then on another machine I forgot that I had the 4LIB loaded via the MMU. Erased the sector
containing 4LIB, which locked up the machine. After reset I enable the MMU, only to
have the machine lock up again. Took me a couple of tries before I realized that I had to clear the
4LIB MMU entry manually before enabling the MMU. I should probably put a note about this in the manual.
YLIB updated to -2H. Fixes the case where if an IMDB? group search was attempted with an illegal group identifier
the machine would exit with the Turbo mode set to 50. Obscure, and not an issue for most people.
Looking into an issue with YFNX. If an IMDB? search is terminated early it seems that the
machine stays in the 50x Turbo mode that is automatically entered for the search. Grr...
Discovered a bug in YFNF-1B. The YPEEK+ and YPOKE+ functions work properly, but don't return the
correct result to the display or Alpha register: the four most-significant digits of the pointer are
reported as "0000" even though the pointer is correct in memory. Fixed in YFNF-1C.
I guess nobody except me is using YFNX... otherwise they would have noticed the minor bug. It's
not really a big deal, but it's fixed now. It has to do with EXCFG/RCLCFG 0 reporting locked pages.
If page 4 is locked it returned a "3" where it should have returned a "4".
One of yesterday's images got modified, so the flash database and the
memory reference got modified.
A few more images added to the memory map. The 3-D printed serial port covers look good, so that's what
I'll be supplying from now on. If you're interested in how the Secure Hash Algorithm works, check out my
article in the September Circuit Cellar magazine.
Check out the HP-16C Emulator Manual for the
lastest of 'Angel Martin's contributions to the 41C universe! Now I only need one calculator (a 41CL, obviously) on my desk.
Nate Martin was gracious to modify his 3-d Port cover model for me to hold the serial connector,
and I have a couple of test articles on order from Shapeways. Yeah! No more spending 10 minutes
each to modify a Port cover (and screwing up about 10% of the time.) But not much progress on the Time
module clone - I've been working on a couple of magazine articles. I did realize that I should use
a different FPGA development board, though, and got the breadboard ready for the change.
Batch of boards is back, and have shipped the first few. Finally got the Timer clone to compile,
(using a non-default synthesis option, thank you) and am almost ready to try it in the breadboard.
Fingers crossed. Also thinking about 3-d printing some Port covers to hold the serial connector.
So the design wouldn't compile using the default logic synthesis tool. Support finally
comes back with "It works fine using this (alternate) tool." Might have been nice to mention that somewhere.
So now the design compiles, and the placement finishes without error, but the routing fails,
complaining about a net that I can't even find in the design. Another question for Support.
It turns out that all of the xxCFG 0 functions have a problem. I inadvertently introduced
the bug when I modified the functions to include Page 4, which requires special handling.
I think that YLIB-2F corrects the issue. Thank you to Christophe Gottheimer for noticing the bug.
There is a bug in YLIB (used by YFNX) around the EXCFG 0 function.
Until I figure out how to fix it, you can work around the problem by always
applying the Lock status to Page 4 before attempting to use this function.
I have to use a different FPGA vendor for the Time module clone. I notice that the
date on the datasheet is recent, so I take a look... and find the statement "Address 0
cannot be initialized" buried in it. This means that the embedded memories need
special handling to be used as a ROM, which is something I need. Incredible, because
this restriction isn't even mentioned in the "Memory Usage Guide." So now I'm
wondering what other obscure notices are buried in the spec. Time for some very careful
Updated the software page to reference .zip files for easier downloading.
Looked at the code for the Time Module clone. My first thought was "Why in the
heck did I do it that way?" After an hour of thinking, I realized that it was
an artifact of my first implementation in CPLDs, which have different constraints
from FPGAs. So now the design is cleaned up and ready to breadboard in a Lattice
Okay, ordered parts for another batch. But now I need to get more
front labels created.
All of the current batch are gone or spoken for. You can still submit an order,
but at this point I don't know when I'll do another batch.
Updated the Image database with two new images.
Added another column to the Memory Reference documents (thank you, Gene).
Fixed some typos (thank you, Gene) and inconsistencies in the Memory Reference documents.
Also discovered that I forgot to include a couple of changes in the Flash image. Grr...
One more revised image.
Wait for it... two more revised images. Down to my last 3 boards. Added
tab-delimited text versions of the memory reference documents.
One new image, plus a couple of revised images.
Updated Memory Reference for V2 boards. IMDB_V2 update to follow.
More new images added or updated.
More new images added.
41CL Memory Functions released to Beta test after I added a few more functions. Updated several manuals for
revised and new images.
Found it. Assembly language can be very unforgiving of typos. (I already knew that.)
41CL Memory Functions is ready for Beta testing.
Still haven't figured out HOW the software bricked the calculator. Very
...and I just bricked my calculator. Debugging time.
Plugging away at testing the 41CL Memory Functions. About half done.
Updated several manuals to include new images. Will load 41CL Memory Functions on a machine
today to see how it works on real hardware.
Preliminary manual for 41CL Memory Functions is available. Code itself is in Alpha.
Updated manuals for PowerCL, SandMath and SandMatrix modules (thank you, 'Angel Martin) are available on the "Documents" page.
I'm now working on the 41CL Memory Functions, which will finally make the Flash Database useful. The lost
package to South Africa was eventually found. Turns out a postal worker strike there meant that over
40 million packages piled up, undelivered.
WARNING! Never attempt to use YFWR or YFERASE on a Flash address
in the OS area, or outside of the valid Flash address range. Acceptable Flash addresses are from 0x008000-0x0FFFFF for
V2 boards and 0x008000-0x1FFFFF for V3 and V4 boards. The Flash address is not fully decoded in
hardware, which means that addresses outside of the normal range will wrap around into the valid range.
In addition, my "fix" for the OS area check isn't quite right.
The newest versions of 41CL Extra and Extreme Functions will do a range check to prevent the problem:
-4E for YFNS and YFNZ, -1E for YFNP and -2B for YFNX.
YFNX-2A seems to work as advertised. Time to start working on the Memory Functions image.
The Post Office finally managed to lose a shipment. Of course it was the one that had a calculator
body plus two 41CL boards in it. To make matters worse, it was going to a destination (South Africa)
where the Post Office will not insure packages. I think I figured out why they won't insure packges
going there. What a pain.
Testing YFNX-2A. The only change eliminates the need to copy the image to RAM
before writing or erasing Flash. Instead, the functions automatically copy a small
section of code to RAM and then execute it from RAM. Uses the existing dynamic
paging code to transiently map the code in RAM to Page 4.
Finally got around to updating the NEWT manual to reflect the final
keyboard scanner fix. Also updated the V2 board memory map and identifier
Total of three boards have issues. One high current (250mA), one where
the Flash doesn't respond to a JTAG query, and one where the running current
is about double what is normal. Strange, this is the first time I've seen
any of these issues.
Arghhh... Seven sectors of Flash need updating on these boards because
of new images. 34 minutes per board over the JTAG port. And then one board
(so far) has some kind of problem that I'll need to debug.
Assembly batch is supposed to be delivered tomorrow.
Latest batch out for assembly. Should be back around 8/10.
Found all of the required parts. Time to start programming the Flash before sending out
for assembly. On another note, after years of manually translating from .rom to Intel hex
(six steps, each using a different program) I finally wrote a translation program for the PC.
I also wrote a program for the PC to calculate the CRC for a .rom file. Why didn't I do this
before? And on yet another note, finally got everything necessary to breadboard the Time Module
Rounding up parts for another assembly batch is getting interesting. Some of the parts
are becoming hard to find. And the price for shipping has increased too. Bummer. On top of
that, my source for Port covers doesn't have any more for me.
Version -1G of the 41CL Extreme Functions and version -2E of the 41CL Library are available. These
versions must be used together because of the change in how the previous Page-4 MMU contents are saved
Okay, the latest version (-1F) of the 41CL Extreme Functions is completely screwed up. I
have reverted to the previous (-1E) version until I get this mess cleaned up. The problem is
with the handling of the Page 4 library.
The latest version of the 41CL Extreme Functions has been released.
Boards are available! Updated YFNX and IMDB are available on the "software" page.
Batch is back from assembly. Will start testing, programming, and soldering the piezo buzzer tomorrow.
Need to verify the turbo/keyboard fix before I can start shipping.
Is this batch jinxed? It seems that DigiKey shipped the wrong parts for one
device - but had the catalog number correct on the parts bag. So now the assembly
is on hold until I can get the correct parts to the assembly house. In addition
to messing up my schedule, it has inconvenienced the assemby house. They
only noticed the problem because the package had the wrong number of pins. What
if this happened on a passive part? That would be tough to track down. What if
the wrong voltage regulator (in the right package) was shipped? That would
fry the board. Arghh.....
Another batch is out for assembly. I found a source for 9-pin null-modem
adapters, so now you don't need a special cable for CL-CL transfers. Just use
the null-modem adapter to connect two normal CL serial cables.
I have updated
the order form: it's now a fillable pdf (a big thank you to Caleb Brown).
I still haven't found time to look into the keyboard issue with Turbo mode. Also,
a problem has been reported with the YIMP/YEXP functions in the 41CL Extreme
Functions, and I still need to look into that.
It seems that the fix for the two-key rollover makes the keyboard
miss keystrokes if you are running faster than 1x. This is only a problem
in images that prompt for keyboard input while in Turbo mode. None of the
native OS functions or 41CL Extreme Functions have a problem because in
these cases the keyboard scanning is always done at 1x, even if a Turbo
mode is active. I am investigating.
All of the latest batch have been sold. I'll still accept orders,
and once I have enough accumulated I can start another batch.
Updated the "pc41.txt" Ruby script
(thank you, Geir Isene) for serial transfers.
Updated the documentation on the "Manuals" page again. Added link to "clio.py" software
(thank you, Bernd Grubert) for serial transfers.
Updated the documentation on the "Manuals" page to reflect the latest software. Also
added links to documentation for some other images (thank you, 'Angel Martin) on the "Other Docs" page.
Two of those "spoken for" V4 boards are now available to anyone who wants them. I also have
one V3 board and at least one V2 board. The difference between V3 and V4 is only relevant if you
plan to do a direct 41CL-to-41CL serial transfer, or if you plan to solder a time module to the
connection points on the top of the V4 board. All of my personal machines use V3 boards.
All of the current batch are theoretically "spoken for" but I need to verify that. I'll still
accept orders, though, for when I do another batch.
Sent out the 41CL Extreme Functions for beta testing today. Only a couple of boards remaining from the latest batch.
Preliminary spec for new 41CL Extreme Functions.
Boards are all programmed and ready to go. Over half of this build has already shipped. I still
need to make some more serial connectors though.
One more function to write for the new Extra Functions version. Yes, it's the most complicated one, of course.
In the process of working on this last function, I discovered that I have been misusing one of the mainframe
subroutines. So the existing YPEEK function may behave strangely if a printer is present. I don't have a good
enough handle on how the XAVIEW subroutine actually works to say more than that right now.
Boards are back. Started programming the logic, connecting the piezo, and updating the Flash.
Still working on new Extra Functions. Two more functions to go (but they're the most complicated.) I
really should update the documentation so that users can review it.
Boards are on their way back from the assembly house in Colorado.
All of the new Extra Functions are done except for the most complicated one: the
new versions of the PLUG functions. Argh.
The latest batch is at the pick-and-place machine. On schedule.
I've been working on enhancing the 41CL Extra Functions, hoping to use dynamic paging
to switch in big code blocks to Page 4 for execution. Incredibly, it seems to be working!
In parallel, I need to write the spec for the new version, for user review.
The latest batch is out for fab. Only 25 boards this time. This revision adds a connection
between the fpga and the serial driver, so that software can force the serial driver on.
This will make CL-CL transfers possible, as long as at least one of the CLs has this ability.
I also added solder pads to the top of the board for the 41C bus signals. This will make it easy
to connect a time module clone.
Well, the cost of the components only went up by 2% overall, even though the FPGA
went up by 8% and the static RAM went up by 19%. So I guess the rule is that cheap stuff
gets cheaper and expensive stuff gets more expensive.
The quote for assembly of another batch of boards is 30% higher per board than the
last batch. Ouch.
I have added a link to a .zip file with all of the Verilog source files on the "Hardware"
page. This should guarantee that the design will survive me. You may or may not like my
Verilog coding style, but this is what works for me. I am happy to answer questions and listen to
suggestions, but make no promises about responding if the required bandwidth becomes excessive.
So, while looking at the Verilog code to figure out a way to force the RS232 driver
on I finally realized why the SERINI doesn't set the baud rate to 1200 like it's supposed
to. I properly initialized the baud rate generator with the right value, but forgot to initialize
the reload value with the right value. Rookie mistake. But I don't think I want to mess around
with the FPGA programming just for this.
All of the boards from the last production batch are spoken for.
I'll start a waiting list for any future orders.
All but one of the boards from the last production batch are spoken for.
Also, I still have one V2 board. I'll start a waiting list for any future orders.
The 41CL manual has been updated, incorporating the various application
notes that have been generated in the past. I also cleaned up the formatting
and reorganized the chapters to make it look more "professional".
In case anyone is interested, Circuit Cellar magazine interviewed me for their 25th
Anniversary issue, available at the
Circuit Cellar Webshop. I wrote about the 41CL project in the October 2010 issue of the magazine.
Okay, the keycode test in the service module now passes on my machine. 2-key rollover works as it should.
I think that I have a solution to the 2-key rollover issue (at least it works in the simulation).
Since this means an update to the FPGA programming I may also add banking for Page 4 at the same time.
The routines for dynamic paging fit into space available in the X-Functions image. If you are interested,
the source code is available on the "Software" page. Comments are welcome.
Added a release note about the 2-key rollover.
I've started working on some software
that will implement dynamic paging of memory. This will allow software to switch in pages of code
during a program to provide more code space (or common subroutines) as necessary for a function.
This will allow me to add much more complexity to the 41CL Extra Functions if I need to. I am
also thinking about implementing a "CAT 7" function that will catalog the current MMU programming,
much like 'Angel does with his MMUCAT function.
New manual and 41CL Extra Functions -4C posted to site.
Arrrgh... I just found out (thank you 'Angel) that one of the images is improperly placed in Flash
in the V3 boards. I have created a procedure to repair the problem, located here.
I have also been notified (thank you Sylvain) that the PEN and LORG functions in the Plotter module don't seem to
work correctly. I don't have a way to test this myself, so I'll have to wait for further word from users.
YFNZ-4C (to fix the last "hidden flag" problem) should be ready shortly.
I have just been informed that my fix for the "hidden flag" problem does not work when the
calculator shuts off automatically after the ~10 minute time-out. I didn't think about this case
when I was crafting the fix, obviously. This is probably going to be a royal pain to fix, but
I'll keep you informed here.
Updated the 41CL Calculator Manual to fix a number of typos.
Updated the 41CL Calculator Manual to include YCRC results.
Updated the 41CL Calculator Manual with some new images.
Also updated the Image Identifier table with some new mnemonics.
Any future orders will ship with these pre-installed.
YFNZ-4B and YFNP-1B are available on the "software" page.
I think I have a fix for the "hidden flag problem". The technique will also make it
so that the current Turbo state is saved during Deep Sleep (when the calculator is turned off.)
This means no more patching YFNS if you want the calculator in a specific Turbo mode at
turn-on. The changes will be in a new YFNZ-4B and YFNP-1B, to be posted here as soon as I
have verified proper operation.
I have just been informed that the 41CL does not properly preserve a trio of internal
flags when the calculator is turned off. These flags are stored in the upper bits of the
ST register in the CPU. I had erroneously thought that all status information was mirrored
in memory during deep sleep. The flags are: The flag that signals that the program at the
program pointer is PRIVATE, the flag that signals that the program at the program pointer
is in ROM, and the Stack Lift Enabled flag. Saving these flags in hardware is probably not
possible, given that they would have to be moved to the CPLD portion of the design, so I
am currently looking into a software way to save/restore the flags during deep sleep.
Since this is the first I have heard of this issue, I assume that it doesn't affect most
users. I will keep everyone updated here as I work through the issue.
I have 15 boards ready to ship. The final 24 boards need to be programmed and have the
piezo buzzer soldered to the board. I also need to make the last batch of serial connectors.
I still haven't decided whether it's worth it to build time module daughter boards.
Added a document about automatically enabling Turbo mode in the "Other Docs" section. Also
updated the module mnemonic matrix with the "4SMT" (library-4 Sandmath)
mnemonic. I'll add this image to the current run of boards.
Batch is back from assembly. I plan to start programming/testing this week.
YFNS-4A and YFNP-1A officially released.
Final (really) write-up about the Image Database released on the "Other Docs" page.
Now I need to generate a document with all of the YCRC check values for the Flash contents
and update the documentation with any new image mnemonics.
Final write-up about the Image Database released on the "Other Docs" page.
YFNP-1A (41CL Extra Functions Plus) is ready for Alpha test. Send me an email
if you would like to get a copy. Source code and a .ROM image are available.
Added a write-up about the Image Database to the "Other Docs" page.
Added the POWERCL documentation (thanks 'Angel) to the "Other Docs" page.
Still pondering whether or not to do another build...
All 50 boards have shipped or been spoken for.
I'll be adding a section to the manual about how the Image Database works shortly. This will make it easy for
users to add their own mnemonics. I'll still keep the "official" list for newly-released images, so that new
users will have a known starting point for the database.
So far 44 boards have shipped or been spoken for. Perhaps the market for 41CL calculators is now saturated,
so I'm not sure about doing another batch.
I received a development board for the new Lattice iCE40 FPGA series, so I'll try to load the Timer chip clone into it to see
if it fits (and works). If the design fits into one of these parts it might be possible to squeeze a Time Module
clone into a module housing, but I don't know if I really want to go in that direction, because it means destroying
what is probably a perfectly fine module just for the housing.
Release notes updated. 34 boards shipped so far. The Time Module clone is ready to fab, but I suspect that
it is going to be too expensive using Xilinx CPLDs. The new Lattice parts look very attractive, but when will
they really be available?
The 4 reworked boards are back from the assembly house. They replaced the power-supply controller
(just in case it was damaged by the shorted inductor) and the inductor. Need to test them tomorrow.
Caught up on orders for this batch: 30 shipped. Still need to find homes for 20 more.
If you're interested, this is where the 41CL boards have found homes.
So I bought an IR thermometer to see where the high current was flowing in the 4 failing boards.
Scanning the board revealed just one hot spot: the inductor in the switching power supply. Hmmm...
everything looks okay, so let's compare this board with a good one. Incredibly, the inductor on the
failing boards is placed rotated by 90 degrees! The 4 boards go back to the assembly house for rework
I sent 41 notices out that boards were available. 23 people responded with orders for 27 boards.
3 people said no thanks and 16 didn't repond. That's a slightly lower response rate than in the past.
Ordered more Port covers and serial cables just in case more orders come in.
46 boards ready to ship. 4 boards failed because of excessive current. I need to investigate this
before I order another batch.
First board from this batch seems to work fine. Piezo buzzers soldered. Now I need to
program all of the FPGAs.
Cleaned up the "Release Notes" page on the website.
PC boards are back from the assembly house. Will program the hardware and solder the piezo buzzer on one board to
start the verification tomorrow. Assuming that everything works, I'll start on the remainder of the batch and start
notifying people on the waiting list.
Spent the day assembling 50 serial connectors. Now I can't straighten out my back or focus
my eyes beyond twelve inches.
I ordered 50 FPGAs from DigiKey, and the anti-static bag said that there were 50 pieces inside.
But when it was opened at the assembly house there were only 49 inside. So the job went on hold for
the three days it took me to get them one more piece.
Spent all day yesterday programming the Flash memories for another batch. It sure would be nice
to have a gang programmer instead of having to do it one-at-a-time. Parts shipped to the fab house
There is an error in the first release of the Image Database. The entry for the MADV mnemonic is incorrect. The correct value for this
mnemonic should be 40F8 (not 207C). The IMDB files on this website have been updated.
I just discovered that the YFWR function does not prevent writing to the OS area! So be warned that you should NEVER
try to write to the OS area of the Flash, or you will brick your calculator like I just did.
This warning applies to ALL versions of YFNZ prior to -3B.
Oops. Not enough testing. Posted fixed yfns-3a to site.
Posted yfns-3a to site.
The FPGA programming change to support banks in Pages 6 & 7 fits in the device.
Just need to verify that it works correctly.
The FPGA programming change for the HEPAX DISASM issue has been verified. The FPGA programming change
to fix the OS mapping function has been verified.
Preliminary schematic for Timer Module replacement completed and posted.
V3 Flash image built. Components ordered.
Updated manual, covering YFNS-3A and V3 hardware, posted to site.
This time around I'm not going
to notify people until I actually have boards ready to ship. The stress of trying
to debug boards after people had already paid was too much.
Just to be clear, the Version 3 hardware does not include the timer functionality.
It does double the size of both the Flash and the RAM.
I am going to try to design a separate time module replacement board. The design rules for
the BGA packages are a LOT tighter than what I used on the 41CL boards, and I don't want to have to
fabricate the entire 41CL board with those tighter ($$$) design rules. There isn't
room on the 41CL board for all of the packages required for the timer anyway.
41CL Version 3 PC board released for fabrication.
The time chip design requires three CPLDs,
each in an 8mm x 8mm BGA package. A pair of XC2C256 devices and a single XC2C128.
One "256" device is 95% utilized, containing channel A. The other "256" device is
89% utilized, and contains channel B. The "128" device contains the bus interface and
is 75% utilized. I would use a "512" device instead of the pair of "256" devices, except that the package options are all
physically too large. This is a full implementation of the HP spec except for the
start/stop inputs, which are not used in the Time module. The interface CPLD can also be used wth an implementation
that uses a microcontroller for the timer functionality.
The version 3 board design is complete and checked. Hopefully this will
be the final version. Since there are about 35 people on the waiting list, I'll
probably start another batch shortly after I get the bare PC boards back.
Added updated manual for YFNS-3A to the website.
YFNZ-3A is almost ready to release to testing. Cleans up the error handling, removes the need for patching
when loading via other than the serial port, uses the image database for the PLUG functions, automatically copies at 50x turbo,
outputs a status message during long operations, etc. Will be updating the manual with the changes next. Still need to check the
new board layout before sending it out for fab.
The problem with the MAPEN function is hardware-related. The issue with the HEPAX DISASM function
can be repaired with a simple patch. See the new "Release Notes" page.
User feedback says the accuracy factor feature in the timer chip is important. That may mean
no timer chip clone in a CPLD. C'est la vie.
Oops, the timer chip actually requires 506 flip-flops. Trimming the accuracy factor logic, which
I suspect that not everyone uses (I know that I haven't used it) means it should fit in the XC2C512,
but there is no way this device will fit on the 41CL board. An XC2C384 might fit, if it replaced the
current CPLD, because it comes in a TQFP144 package. But that would limit me to about 320 flip-flops.
That limit would compromise the functionality.
On a more positive note, I am just about done
with the circuit board modifications.
The timer chip requires 326 flip-flops, which means that it MIGHT fit in a CPLD. But I don't
see a way to include the functionality on the 41CL board itself. There just isn't enough room on
the board for another package, especially one that is 17mm square (this is the smallest package
for the biggest CPLD). So don't everyone get your hopes up.
Theoretically I could just replace the
current CPLD, but the new package is BGA, which is going to mean more layers on the PC board, and my
board layout tools only support up to the four layers that I currently use. Upgrading the board layout
tools is expensive, so that is not likely to happen.
Clone of the timer chip seems to work in the simulation. It was a nice challenge to guarantee
that time is kept properly independent of deep sleep/light sleep/run state. It's interesting that
the HP spec for the chip is 30 pages, but the Verilog code for the design only requires 12 pages. Now
I can get back to revising the printed circuit board layout and then think about starting another batch.
Almost done with a clone of timer chip. Still need to finish board layout modifications and decide
whether or not to order a new board revision. I should probably start thinking about modifying YFNS to use the Image Database.
48 boards have shipped. I have one board that can be soldered in place rather than using the
press-fit connector. I soldered this board to my test calculator for debugging, so the connector land pattern
is pre-tinned, which makes the surface uneven and unsuitable for use with the press-fit connector.
Contact me if you are interested.
Started modifying the PC board layout to add a dedicated pull-down resistor so that I don't
need to manually solder a jumper on the board. Considering other modifications at the same time:
1. Route two extra address lines to the Flash memory to allow for a 2x or 4x larger Flash?
2. Route an extra address line to the RAM memory to allow for 2x larger RAM?
3. Add three extra connections between the FPGA and the CPLD, just in case? This would allow one
more status bit to be stored in the CPLD, which would retain the status while the calculator is
Total of 42 boards have shipped. Slow going now because I have to notify people
two or three at a time to make sure that I don't over-commit. Still seeing that
one out of three people don't even bother to respond one way or the other.
Now I need to decide whether to do a build of 25 using the remaining bare boards or
go ahead and revise the board to avoid soldering the jumper (hoping that I can sell more than 25).
Started notifying the next people on the waiting list. There are 11 boards remaining.
The December issue of Circuit Cellar magazine has an interview of me if anyone
is interested in learning what makes an IC designer tick.
Caught up with orders, with a total of 33 boards shipped. 14 people didn't respond
with an order, so they lost their place and the next people on the list
will be notified shortly.
10 boards shipped today. Invoices are out for 3 more, awaiting payment.
11 boards shipped today. I hope to be able to catch up tomorrow. As with
the beta boards, only about two-thirds of the people who said they were
interested actually respond when I send them a link to the order form. I'll
probably offer the unclaimed boards to the next people on the waiting list
at the start of next week.
I can only solder about 7-9 jumpers before my hand gets too shaky to be
successful. So 7 boards shipped Saturday, and 9 will ship tomorrow. Plan is
for another 8 or 9 on Wednesday. Then I'll be caught up.
Repairing the boards requires just a single jumper. I plan to start shipping
A single pull-down on PWO_HI should be sufficient, since this is the master
reset for everything on the HP-41 bus. I was originally targeting the clocks because
those signals go through vias, which are easy to solder to. But PWO_HI should be
the correct fix. It's just a little harder to solder to. Will verify tomorrow.
Resistors arrived today. Reprogrammed the CPLD and FPGA for half of the
batch. Still need more testing on the fix, but looks good so far. I probably
just jinxed everything by posting that.
It may require three resistors for a guaranteed fix. Pull-downs just
on PH1_HI and PH2_HI make the board start up properly 99% of the time. But
I may also need one on PWO_HI for the final 1% case (where the calc has been
off for a long time and the start-up delay is slightly longer). It will always
start with a second press of "ON", but I haven't yet checked it with the Time
module installed. Resistors should arrive tomorrow or Wednesday.
1. Just because it worked once doesn't mean it will work again.
2. Low-power design is tricky. (Duh. I already knew that.)
3. You can't fix everything with programmable logic.
4. It's good to have signals go through vias, for soldering patches.
5. Always bring unused CPLD and FPGA pins to vias too, for potential future use.
6. Always provide extra connections between the powered (CPLD) logic and unpowered (FPGA) logic.
7. The right tools (e.g. a mixed-signal sampling scope) make debugging easier.
8. Never assume. Completely test one board before programming the rest of them. (Duh. I already knew that too. Shortcuts can be fatal.)
CMOS chips have an "activation" voltage, related to the transistor
threshold voltages, below which nothing works. This batch of FPGAs has
an activation voltage higher than that of the level shifters used to create
the 41 bus signals. As a result the level shifters start operating prior
to the FPGA outputs being valid. In my defense, I don't have a mixed-signal
sampling oscilloscope, which would have made the problem obvious.
The addition of two pull-down resistors should solve the problem. The pull-down
resistors in the FPGA don't help because they really aren't resistors, so
they don't start "working" until the FPGA activation voltage is reached.
Using an output from the CPLD to disable the PWO output from the FPGA
during deep sleep doesn't help. That means that the problem is most likely occurring during the
time before the power supplies are stable, while the FPGA outputs are
supposedly "floating". Time to try the programmable pull-downs on
the FPGA pins.
The logic in the CPLD assumed that PWO and DPWO would not be
active while the board was powering up (which is the correct behavior). I
have modified the CPLD logic so that the state of these two signals
is ignored during the power-up time. Now I need to try to modify the
FPGA logic to somehow make the PWO output stay Low while the reset
signal is active (like it's already supposed to do).
This is incredibly frustrating. If I have to scrap this batch I won't
be able to afford to build another.
The thing works fine except when waking up from deep sleep. PWO
goes High for no reason, despite the fact that the reset signal is
active, supposedly holding the flip-flops static! This throws off
everything, because the entire system is synced to this edge.
It would be nice if the effing FPGA would operate properly. During
power-up the reset input to the FPGA is held active for several
milliseconds after the power is stable. But this batch of FPGAs
appears to completely ignore that fact, and signals that come from
flip-flop outputs (supposedly reset) are High! WTF? This messes up
everything, because the logic assumes that a couple of these signals
really will be Low during reset.
The start-up of a beta board is a thing of beauty. From zero to
full speed with nary a glitch. With this batch the start-up is a
complete mess... start-stop multiple times. Weird ISA bus timing,
PWO toggling... No wonder there's a problem.
The boards are failing the final test. WTF? I guess that's what
happens when you accept orders before final test. I should know
UPDATE... seems to be related to fast OFF-ON issue noticed with
the beta boards. Time to get to the root cause. Some kind of race?
Flash update is taking 25 minutes per board because of the solution
FPGA programmed on all boards.
CPLD programmed on all boards. FPGA programming next. Flash
update image ready (unless there are more solution books).
Piezo buzzers and power connections done on all boards. CPLD
programming is next.
Serial connectors done. Port covers modified. Piezo buzzers and
power connections are next.
First batch of 50 is back. Working on making the serial connectors.
Need to also mount the piezo buzzers and program the CPLD and
FPGA on each board, update the Flash, plus a quick final test.
Each serial connector takes about 10 minutes to make. Then another
10 minutes with the Dremel tool (using three different heads) to
modify the Port cover. Mounting the piezo buzzer and power wires
for programming is about 3 minutes and CPLD/FPGA programming
takes 5 or 6 minutes. Updating the Flash takes about 11 minutes.
Multiply by 50 boards. This is why it's taking so long.
First batch of 50 out for assembly. Time to solder some
Added documentation for Production version. Parts for the
first batch of 50 have been ordered. We expect to have
boards available early in October.
Added document describing hardware programming.
Fixed the .rom files here so that no patch is required for
YFERASE and YSEC when running in Turbo mode.
Simulated fast OFF-ON sequence. All waveforms look fine.
Must be something undocumented in the timer chip?
Beta status document updated with yfns .rom file patches.
Revised YFNS to revision 1E. Added files section to website.
Second report of a problem with YFERASE. Until further notice
I recommend not using the flash functions.
WROM instruction fix verified. Compiled logic fits in FPGA. Need
to verify on a board. Flash update image built.
Revised YFNS to revision 1C. Will try FPGA update to fix WROM
instruction later today.
Updated 41CL Manual to include OS register usage.
The sample labels arrived. Here's what my finished
41CL looks like.
The last two boards shipped today. Thank you to all of those who took
a chance and ordered one. Here is where the 21 boards found homes:
Australia (x2), Canada, Canary Islands, England, Finland, France,
Germany, Italy (x2), Norway (x2), Singapore, Switzerland (x3) and
the USA (x5). (Plus the one I kept for myself, the development board,
the two that got smoked during testing, and the two Alpha boards.)
Three more boards shipped today, for a total of nineteen. Modified my
last three Port covers. Hoping to find homes for the last two boards.
Updated manual with part numbers for do-it-yourself serial connector.
Added final schematic to website for reference.
One more board shipped today. First user feedback is positive. Yeah!
Three more boards shipped today. Several have already arrived at their
Three more boards shipped today. Eight remaining to go.
layout for 41CL label samples. Feedback welcome.
Nine boards shipped today. By not responding with an order form,
five people lost their spot on the "top twenty" list today.
Ten invoices sent. Will start shipping Monday! Finally, the end
of the project is in sight.
Ten port covers modified for serial connectors. Should finally be
able to put away the oscilloscope, logic analyzer, power supply,
programming cables and soldering iron. :-)
Flash updated on all boards (65minutes/board x 22 boards).
Twenty-five serial connectors soldered. Still need to modify Port
covers. Trying to figure out international shipping (a royal pain).
CPLDs programmed on all the boards. Lost one board due to "bad id"
returned from CPLD during programming. Another $200 up in smoke.
FPGAs programmed on all the boards.
The first thing I always asked a customer with a problem was "Did
you read the datasheet?" I swear I read the datasheet, but that was
a couple of years ago. Duh. I forgot that the JTAG reset signal was
active-low. So now I can update the Flash memory with the final
software. Sent the order form to the lucky 20 people who were first
Still can't get the JTAG programmer to talk to the JTAG chain on the
board. Either there is something magic involved or I am overlooking
something very basic.
New flash images are ready and the JTAG configuration files are all
set up. Too bad I can't get the effing JTAG programmer to talk to the
JTAG chain on the board.
The Flash functions (Erase and Write) in the 41CL Extra Functions
don't work, because of a stupid coding mistake. Sorry, I'm really
a hardware guy. Now I have to find a way to make the corrections
fit. On the bright side, this should be the last of the changes to
this code, as everything else seems to work okay.
41CL manual updated with changes to be applied before release.
Still need to try out revised Y-Functions in emulator.
Might be able to try JTAG reprogramming of Flash tomorrow.
Piezo buzzer and power wires for programming soldered to all 23
PC boards and I only dropped the soldering iron on my leg once.
I'm sure that I'm working for Bangladesh wages on this project.
New Flash image built except for revised Y-functions. Six new ROM
images and six updated ROM images. Need to finalize Y-functions
and then try to reprogram the Flash via JTAG. Cross your fingers.
YGET (serial input) now works properly.
Still not sure how to test YIMP (serial block input).
Hardware issue was improper handling of register address in some
cases. Logic got broken when I modified the logic to make register
reads and writes run at turbo speed, rather than always at 1x. Oops.
JTAG programmer should arrive tomorrow. Working on generating the
configuration files necessary to try to program the flash via JTAG.
Planning on modifying Y-Functions to include a couple of new images.
YGET still doesn't work correctly. More investigating.
Buffer functions work, but have to restrict to physical addresses.
Also have to restrict export and import to physical addresses.
Incredibly, something has broken User mode. More investigating.
Tired of keying in patches, so I've ordered a JTAG programmer for
the Flash memory.
Found the issue with the YGET (serial read) function, and it's messy
to fix. Requires 16 more locations be patched, so I'm afraid I'll have
to do the patches myself for the boards and write the code to an open
slot in the Flash. I wish JTAG programmers weren't so expensive,
because with that I could just reprogram the Flash in one shot and
even add new images before release. Oh well.
PEEKing and POKEing confirms that the serial receive hardware is
working correctly (yea!) so now I need to figure out what's wrong with
the YGET (serial read) function. I still don't know how to test the
YIMP (serial block import) function. Need to expand the manual with
the various things I've noticed, like YGET doesn't pop the fifo in the
case of an overflow, so you need to do SERINI to clear an overflow.
Duh. The RS232 chip automatically shuts off with no valid level on the
RX input. Serial port transmitter works. YGET function (serial receive)
always returns indicating overflow for some reason. Investigating.
Updated NEWT manual for I/O Port operation.
Serial functions need twelve locations patched. Perhaps too many?
Okay, serial port sends out of the fpga... but doesn't make it
through the rs232 driver? Transmitter sends two stop bits, which
is okay (something I forgot, obviously). Baud rate is correct, but
there are gaps between chars when running 1x, which was expected.
Version 2 boards draw only 110uA in deep sleep. The changes made
from the initial version to reduce deep sleep current draw worked.
Found another bug in the serial functions. More patches to come.
Updated the 41CL manual with a section on patching code.
Updated NEWT microprocessor manual for start-up delay.
Well, each of the serial functions have some kind of problem. That's
the problem with using an instruction simulator to check code. Now
I could correct most of them by changing the hardware, but even if
I did that, there would still be at least one patch required. Trying
to decide which way to go... leaning towards just issuing a set of
patches, but first I need to verify the hardware.
Version 2 boards now appear to be working and stable. I changed
the voltage regulators (for lower quiescent current) on version 2,
and they start up more slowly. So the start-up delay in the CPLD
was releasing reset before the FPGA power was really stable, which
led to the PWO logic not always working correctly.
Since I wasn't sure that this was the only problem, I also modified
the PWO logic to eliminate a gated clock. This means a little bit
more power, but the logic is much more tolerant of timing issues. It
also helps the synthesis and routing, as the tools seem to have a
harder time dealing with multiple clock domains.
So now I just need to go through some final checks (mainly the serial
port) before I start programming the boards for general release.
Issue appears to be related to the timing of PWO and/or DPWO on
start-up. The fail cases have these signals rising with the first
edge of PH1, which isn't how the logic is supposed to work. And
it means that the display driver is out of sync with the CPU,
which explains the garbage display.
Second board isn't working. Time for debug. Had to add some
circuitry to account for potential skew on the reset input.
Also corrected a couple of flip-flops that were not being
initialized by reset. These were _probably_ the source of the
start-up flakeyness, because they could lead to the turbo
control getting confused.
Went through the entire design with a fine-toothed comb.
Amazing how many little things ("what was I thinking?") one
can find going back like this. Everything should be solid now.
But then the design tools decided to stop working (aborting in
the middle of a step). After a week of hair-pulling, I started
a new project from scratch in a new directory. It now compiles,
so now we'll see if it works or not. Stay tuned...
UPDATE... the new project failed to import the pin assignment
list properly (and I didn't check it) so the development board
is toast. I hope the display driver on the calculator main
board wasn't affected. Grrr... $200 up in smoke.
Several of the changes made during debugging did not properly
account for clock-domain crossing. Working on fixing these.
Want the boards bullet-proof before release, so be patient.
Problem occurs less often with logic recompile. WTF.
The "flakeyness" that I saw in the test calculator is something
in the FPGA. About 20% of the time turning the machine on will
cause the main state machine to go awry. This never happened in
the rev 0 boards. Now, the code did change, to support internal
code for Page 5, but the code ran fine on a rev 0 board. Time
for some serious debugging.
Something flakey with a Rev 1 board in my test calculator.
The Xilinx programmer fried the mouse port on my computer.
Notified of an error in one of the ROM images. Time to write
a "How to Patch Code" chapter for the manual.
Not a good day.
Assembled boards are back, ready for final debug. If you have
already asked me to put your name on the "interested" list,
I'll be contacting you shortly. All of the boards are spoken for.
Remember that these should be considered "beta test" units, so
if you really don't want such a unit, let me know so that I can
offer it to someone else.
41CL Calculator manual updated with photos.
Finally! Out for assembly.
Final version of 41CL Calculator Y-Functions source code released.
All parts except the Flash memory kitted for assembly.
Manual updated describing how to use Forth image.
Final flash image is built, ready for programming.
Quotes for assembly received. 41CL manual released.
Bare PCBs received. One last update for Flash received.
Service Module reports "CPU OK".
Service Module reports "CPU BAD". Problem is with decimal mode
when inputs are greater than 9. Investigating.
First production PC boards ordered.
HEPAX HEPDIR command works now that WROM instruction is fixed.
WROM instruction is AFU. Perhaps that's why HEPAX doesn't work.
Tech manual updated. Download what is close to the final version.
HEPAX image doesn't work properly. Don't know why yet.
Board design finalized. Board #2 has been in a calculator body,
running off of batteries, for two weeks.
82160A HP-IL Module seems to work. Since I don't have any HP-IL
peripherals the testing was rather cursory.
Going through the board design to try to reduce current drain.
82153A Wand appears fully functional!
82242A IR Module appears fully functional!
Turns out that the IR module expects the CPU to sample the FI
bus during the second clock in a nibble time. (Undocumented)
And the Wand screech and failure during WNDTST was due to an
error in the CLRST instruction.
Oops. Turns out that "WNDTST" only reports the correct data for
the first byte. Second byte is AFU in display, but correct in
the register. This one is going to be hard to find, given that
I can't use V41 to step through code. Hmm...
82143A Printer appears fully functional.
82104A Card Reader appears fully functional.
82182A Time Module appears fully functional.
82153A Wand appears fully functional, but piezo element screeches
during operation. Need to investigate.
82242A IR Printer Module still reports "BAD" with TESTP.
82143A Printer mostly works. "Print" button on printer does not print.
82242A IR Module prints one line, but then errors. TESTP reports "BAD".
82160A HP-IL Module not tested yet.
82153A Wand doesn't start with button press. "WNDTST" mostly
works, but causes piezo element to screech instead of beep.
82104A Card Reader doesn't start up when card is inserted, but does
"VER" on cards, and does write cards.
Time Module doesn't display continuous time with "SHIFT"-"ON".
All of this points to a problem with peripherals pulling the ISA line
High to start the calculator.
May also be issue with instructions executed during SELPRF?
The flag input is active-Low, which I missed in the HP specs. I am
also sampling it during the wrong bit time...
This requires a circuit board change as well as Verilog. The HP spec
also says that the CPU precharges this signal, which I have no way of
doing as it stands right now. Investigating.
82143A Printer catalogs properly, but always says "printer off".
82242A IR Module hangs the machine on start-up.
82160A HP-IL Module catalogs properly, and seems to execute, but
I have no HP-IL peripherals to verify this.
82153A Wand makes the calc start-up wierd, with high-pitched screech.
Catalogs properly, but doesn't seem to work. Also, doesn't start
calculator with press of button on wand.
All of this can probably be attributed to something wrong with the
SELPRF instruction and/or flag input
Buy a copy of the October issue of Circuit Cellar magazine!
My article about the design is there.
Found a source for the CD40109 (thanks Gene), so I'll be able
to do the first production run soon.
Still have lots of things to verify though, by putting board
number 2 in a calculator body to verify operation with things
plugged into the physical ports.
Also need to build the Flash image for the release version.
Deep Sleep: 310uA, Light Sleep: 4.2mA, Run: 7.9mA
Register read timing change verified.
"Loop of addition" benchmark:
Light Sleep current drain reduced by disabling clock.
Register read timing changed to improve Turbo mode
performance. Need to verify.
First production components ordered.
Investigating if it's possible to change the design to do
register writes at turbo speed, which will improve turbo
Also investigating ways to improve Light Sleep current drain.
Found the light sleep current drain - floating data bus.
Deep Sleep: 330uA; Light Sleep: 6mA; Run: 7.7mA (no turbo)
Almost ready to order first production batch!
Light Sleep current isn't from FPGA after all. Still looking.
Software for PEEK and POKE for I/O do bytes. Need to modify to
PLUGx only works correctly with 4K modules. Software issue.
Had to delete 4-byte transmit buffer to make room for changes.
User mode operation fixed. Problem was with c=regn instruction.
PLUG3 issue is a software bug.
Updated spec posted to site.
User mode doesn't work. Machine hung when I tried to PLUG the
Real Estate module into Port 3.
Turbo mode works!!
The MMU seems to work.
Module images can be plugged into ports and unplugged from ports!
Turbo mode does not work.
Still no resolution to the power issue, but problem when eliminating
continuous reset may be due to dpwo signalling with display drivers.
POKE works... just not with an on-chip peripheral address. Grr...
Eliminating continuous Reset during Light Sleep works in sim but not
in the FPGA. More grr...
90% sure that Light Sleep power issue must be due to FPGA being
held in Reset during this time. Hmm...
Added option to enable/disable MMU via peripheral write. Necessary
because of error in the code in Flash. Will test next.
Verified that POKE works. Looks like block copy works.
Fixed Bank Select and Turbo state so they're preserved in Light Sleep.
Still haven't found the light sleep power issue.
Corrected an issue with updating register address and PFAD
Corrected the WCMD instruction write cases, so now POKE works.
Corrected the WCMD instruction read cases, so now PEEK works.
The bank switch bits are not preserved during light sleep. Investigating.
Still haven't changed the clock to stop during light sleep.
Getting POKE to work means that I can now test the Turbo modes
and program the MMU to verify the PLUG and UNPLUG commands!
Model of display chip working. Makes simulation easier. Also means
that I can build an interface to a different display. LEDs?
Oops, the MMU was being disabled by light sleep. That's fixed.
Also the data bus and the isa bus were both being driven during
light sleep. Is that the source of the current drain during light
sleep? We'll see. Need to disable the clock inside the FPGA during
light sleep. That will save 5-10mA.
The flag output wasn't initialized during light sleep or deep sleep.
Since the Actel flip-flops like to power-up holding a one, that
meant the output was always High until a TONE or BEEP. Not sure
how that would affect the piezo buzzer. Fixed.
The problem with running programs has been found. The CLRST
was clearing all 12 bits of the ST register.