Systemyde 41CL User manual

41CL User Manual
© 2019, Systemyde International Corporation 1
41CL Calculator

41CL User Manual
© 2019, Systemyde International Corporation 2
Every effort has been made to ensure the accuracy of the information contained herein. If you find errors or
inconsistencies please bring them to our attention.
Copyright © 2013-2019, Systemyde International Corporation. All rights reserved.
Notice:
“HP-41C”, “HP-41CV”, “HP-41CX” and “HP” are registered trademarks of Hewlett-Packard, Inc. All uses
of these terms in this document are to be construed as adjectives, whether or not the noun “calculator”,
“CPU” or “device” are actually present.
Acknowledgements:
This project never could have succeeded without Warren Furlow’s excellent Web site hp41.org. And even
more important was his SDK41R6 software suite, for code development, and his V41 program for code
debugging. Numerous people have answered my dumb questions on the Web site hpmuseum.org, and the
book “Inside the HP-41” by Jean-Daniel Dodin was invaluable for getting a foothold on understanding the
HP-41 operating system and register usage.
Gene Wright was kind enough to be my voice at the HHC 2010 conference.
‘Angel Martincontributed valuable 41CL-specific software to the project.
Eric Rechlin made the labels for the front of the calculator.
Nate Martin modified his Port cover 3-D model specially for use with the serial port jack.
Benoit Maag provided the photograph of the different connector types.
Geoff Quickfall provided the photographs of the older display driver and corresponding capacitor fix.

41CL User Manual
© 2019, Systemyde International Corporation 3
Table of Contents
1. Introduction ......................................................................................................... 5
Can my calculator be upgraded? ................................................................7
2. Getting Started .................................................................................................... 9
Installing the 41CL Circuit Board ..............................................................9
Initial Software Configuration ....................................................................18
3. 41CL Extra Functions .........................................................................................20
Extra Functions Parameter Passing ........................................................... 21
MMU Functions ........................................................................................... 22
MMUCLR ...............................................................................................22
MMUDIS ................................................................................................ 22
MMUEN ................................................................................................. 22
MMU? .................................................................................................... 23
Turbo Functions ...........................................................................................23
TURBOX ............................................................................................... 23
TURBO2,TURBO5,TURBO10,TURBO20,TURBO50 ................24
TURBO? ................................................................................................24
Plug into Port/Unplug from Port Functions .............................................. 24
PLUG1,PLUG2,PLUG3,PLUG4 .....................................................25
PLUG1L,PLUG2L,PLUG3L,PLUG4L,PLUGP ............................26
PLUG1U,PLUG2U,PLUG3U,PLUG4U,PLUGH ..........................27
UPLUG1,UPLUG2,UPLUG3,UPLUG4 ..........................................28
UPLUG1L,UPLUG2L,UPLUG3L,UPLUG4L,UPLUGP ............. 28
UPLUG1U,UPLUG2U,UPLUG3U,UPLUG4U,UPLUGH ........... 29
Memory Block Functions ............................................................................ 29
YMCLR .................................................................................................. 29
YMCPY .................................................................................................. 30
Memory/IO Read and Write Functions ..................................................... 31
YPOKE .................................................................................................. 31
YPEEK ...................................................................................................32
Memory Buffer Functions ........................................................................... 32
YBPNT ...................................................................................................33
YBPNT? ................................................................................................ 33
YBUILD ................................................................................................. 34
Flash Memory Functions .............................................................................34
YFERASE ............................................................................................. 35
YFWR .....................................................................................................35
Serial Port Functions ................................................................................... 36
SERINI ................................................................................................... 37
BAUD12,BAUD24,BAUD48,BAUD96 ...........................................38

41CL User Manual
© 2019, Systemyde International Corporation 4
YGETLB,YGETUB ..............................................................................38
YPUTLB,YPUTUB .............................................................................. 39
YEXP ......................................................................................................39
YIMP .......................................................................................................40
Miscellaneous Functions ..............................................................................41
YFNS? ................................................................................................... 41
Image Database Functions .......................................................................... 41
IMDB? ....................................................................................................41
Special MMU Functions .............................................................................. 43
MAPDIS ................................................................................................. 43
MAPEN .................................................................................................. 44
4. Error Messgaes ....................................................................................................45
5. Functions Summary ............................................................................................ 46
6. Image Identifiers ................................................................................................. 49
7. Memory Management .........................................................................................61
The MMU and program addresses .............................................................61
The MMU and data addresses .................................................................... 64
8. Programming the MMU ..................................................................................... 67
Library-4 .......................................................................................................67
The FORTH ROM .......................................................................................67
The HP Service ROM .................................................................................. 68
9. Image Database ....................................................................................................69
10. Patching Code ......................................................................................................78
11. Using HEPAX ...................................................................................................... 80
Patching HEPAX ..........................................................................................83
Enabling HEPAX Disassembly ...................................................................83
12. Serial Connector ..................................................................................................85
13. Time Clone Connections .....................................................................................87
14. Updating 41CL hardware ...................................................................................90
CPLD Programming ....................................................................................91
FPGA Programming .................................................................................... 92
Flash Programming ..................................................................................... 92
15. Revision History .................................................................................................. 93

41CL User Manual
© 2019, Systemyde International Corporation 5
Introduction
The 41CL design takes advantage of modern technology to significantly add to the
capabilities of the 41C system. In particular, the 41CL provides the following features:
• All 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 (or our Time Clone
mounted on the 41CL board) is required for full timer functionality.
• Full 600-register Extended Memory is built in.
• Support for the new 1024-register Expanded Memory.
• Over 390 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.
• Turbo mode, which allows the calculator to run at up to 50X normal speed. Actual
values available are 2X, 5X, 10X, 20X and 50X.
• Numerous empty pages (4K in length) of Flash memory are available for non-volatile
storage.
• 122 pages (4K in length) of RAM are available. All RAM is continuously powered.
• A sophisticated Memory Management Unit (MMU) allows full access to the large
physical memory.
• Support for fifteen Alternate Configurations, where each configuration is a compete
set of images to be plugged into the Ports.
• Full bus compatibility for the Ports, allowing the use of any peripheral designed for
the HP-41 system.
• A full-duplex serial port is available when the optional serial connector is used. This
optional connector uses a 2.5mm stereo jack mounted in a blank port cover.

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© 2019, Systemyde International Corporation 6
With these features, however, come some drawbacks:
• Power consumption is higher, at least while the calculator is off or in light sleep
(between keystrokes). Where the original HP-41 required about 10 μA while off, the
41CL requires about 110 μA. This will lead to reduced battery life.
• The original HP-41 could retain memory contents for several minutes while the
batteries were changed. Because of the higher current consumption, the 41CL only
retains the memory contents for a few seconds while the batteries are out. For this
reason, you should probably have an extra battery holder ready to go when changing
batteries.
• The advanced technology used in the 41CL is a double-edged sword. The Flash
memory, as well as the programmable logic devices used to implement the NEWT
microprocessor, only guarantee data retention for 20 years.
The table below shows the typical current drain for the 41CL under various conditions.
The serial port is powered up whenever it is connected to something with a valid signal
level.
No Time Clone installed Time Clone installed
Calculator State Serial port
off Serial port on Serial port off Serial port on
Off 110 μA 3.6 mA 340 μA 3.8 mA
Light Sleep
(between key presses) 3.6 mA 7.1 mA 3.8 mA 7.3 mA
Running (1x) (Note 1) 7.1 mA 10.6 mA 7.3 mA 10.8 mA
Running (50x) (Note 2) 12.1 mA 15.6 mA 12.3 mA 15.8 mA
Flash Erase (Note 3) 46.0 mA 49.5 mA 46.2 mA 49.7 mA
Note 1: Measured during a CAT 2 operation.
Note 2: Measured during a normal (not CPONLY mode) FLCHK? operation. See the
41CL Update Functions for details.
Note 3: This peak current lasts for less than 500 mS.

41CL User Manual
© 2019, Systemyde International Corporation 7
Can my calculator be upgraded?
The 41CL is an upgrade created by replacing the CPU circuit board in a 41C/CV/CX with
the 41CL circuit board. This replacement is only possible for calculators that actually
have a CPU circuit board. The easiest way to tell if this is the case is to look at the HP-41
display. If the light part of the display has square corners, like those shown below, the
calculator is a candidate for replacing the CPU circuit board.
Hewlett-Packard changed the display driver circuitry in the 41 series during production,
and this change affected one component value on the CPU circuit board. The 41CL
circuit board implements the component value used in later production units. Units with
the correct display driver can be identified as follows:
• If your 41C (not CV or CX) has a serial number starting with “1954” or larger it uses
the correct display driver.
• If your 41CV/CX has a serial number starting with “2003” or larger it uses the correct
display driver.
It is theoretically possible to use the 41CL circuit board with the older display driver, but

41CL User Manual
© 2019, Systemyde International Corporation 8
this requires soldering an extra capacitor to the calculator main board. Refer to the next
section for the details.
In addition to the display driver change, Hewlett-Packard also experimented with
different methods of connecting the CPU board to the main board. Unfortunately it is not
possible to identify units that used these different connection methods via the serial
number. Identifying such a calculator is a step in the installation process covered in the
next section.

41CL User Manual
© 2019, Systemyde International Corporation 9
Getting Started
The 41CL circuit board is designed to be a drop-in replacement for the original CPU
circuit board, and the installation is not difficult. However, certain precautions must be
taken to prevent damage to both old and new circuitry.
All integrated circuits are susceptible to damage from electrostatic discharge (ESD). If
you have access to an electrostatically protected work area by all means use it. If not,
make sure that you ground yourself immediately before starting the installation process.
The best way to keep from generating a static charge is to not move around while
working, so make sure you have everything required before starting the process. Do not
touch exposed conductors, and handle both the original CPU circuit board and the
41CL circuit board by the edges. The 41CL circuit board has a 2mm space around the
edges devoid of circuitry or components to facilitate handling in this manner.
Tools required for the installation are a small Phillips-head screwdriver, an Xacto knife or
similar, a pair of tweezers, and a small flashlight.
Installing the 41CL circuit board
Follow the steps below to perform the installation:
1. Read through all of these instructions before starting the installation process, to make
sure that you understand each step. We are not responsible if you damage or ruin
your calculator or the 41CL circuit board while attempting this installation.
2. Verify that your calculator is one that has a CPU circuit board. Only calculators with
“square corners” on the LCD display panel (refer to the Introduction section for a
picture) have CPU circuit boards.
3. Remove the battery case, by first sliding the case towards the top of the calculator until
the bottom end of the battery case pops free. Install fresh batteries.
4. Carefully remove the four rubber feet, using a pointed knife to pry up one corner of a
foot and a pair of tweezers to lift the foot from the case. Be careful not to damage the
feet, as replacements are difficult to find. They are attached to the calculator body
using double-sided tape which can usually be reused.

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© 2019, Systemyde International Corporation 10
5. Remove the four screws located in the recesses under the rubber feet. Be very careful
not to lose them, as they are essentially impossible to find unless you want to buy
10,000 of them. The screws are all #2-28 trilobular thread-forming types. Those at the
bottom of the case are 1/4” (they may be 3/8” if the calculator has been serviced),
while those at the top of the case are 3/4”.
6. Lift off the bottom case and the U-shaped center case section. Note the orientation
(front-to-back) of the center case section, because it not symmetric. Don’t worry if
your old CPU board looks slightly different from that shown in the picture below.
These boards went through several revisions during the life of the 41C series.