D-209 === > Summary: Answers to Frequently Asked Questions about HP48 calculators Followup-To: comp.sys.hp48 Organization: GMI Engineering & Mgt. Institute, Flint, MI Archive-name: hp/hp48-faq/part3 ********************************************************* HP 48 S/SX/G/GX Frequently Asked Questions List ********************************************************* PART 3 of 4: Appendices A - H Currently Maintained by: Keith Maddock (madd0118@nova.gmi.edu) Originally Compiled by: Darryl Okahata Key: ! =new Q/A + =revised answer PART 3: * Appendix A: ASC-> and ->ASC functions: * Appendix B: Using non-HP RAM cards in your HP 48SX: * Appendix C: What's new in the HP 48G/GX * Appendix D: The EquationWriter Bug & Rev J Bugfix * Appendix E: Compact Data Storage: * Appendix F: Various useful functions * Appendix G: Rotation rate to angular frequency conversion bug ! * Appendix H: How to make a Serial Cable for your HP48 ****************************************************************** * Appendix A: ASC-> and ->ASC functions: Note: Since this appendix was written by Bill, I dare not modify it. However, I wish to note that ASC-> and -ASC do work on both the SX and GX versions. From: billw@hpcvra.CV.HP.COM (William C Wickes) ASCII Encoding HP 48SX Objects Sending an HP 48SX object via electronic mail can be difficult if the object does not have an ASCII form, such as is the case for library objects. There are various encoding schemes available on different computer systems, but these require that the sender and receiver have similar computers, or at least compatible encode/decode schemes. The programs listed below perform the encoding and decoding on the HP 48SX itself, which has the advantage of being completely independent of any computer. The programs are nominally called ->ASC and ASC->. The former takes an object from the stack and converts it to a string, in which each nibble of the object and its checksum is converted to a character 0-9 or A-F. (The object must be in RAM, otherwise a ROM Object error is returned.) For sake of easy inclusion in email letters, the string is broken up by linefeed characters after every 64 characters. ASC-> is the inverse of ->ASC: it takes a string created by ->ASC and converts it back into an object. When you transmit the encoded strings, be sure not to change the string; ASC-> uses the checksum encoded in the string to verify that the decoding is correct. An Invalid String error is returned if the result object does not match the original object encoded by ->ASC. When you upload a string to your computer, use HP 48 translate mode 3 so that the HP 48 will convert any CR/LF's back to LF's when the string is later downloaded. Two versions of ASC-> are included here. The first (P1) is in HP 48 user language, using SYSEVALs to execute system objects. P2 is a string that the setup program uses P1 to decode into an executable ASC->--then P1 is discarded. The second version is more compact than the first, and also uneditable and therefore safer (but it can't be transmitted in ASCII form, which helps to make the point of this exercise). Here are the programs, contained in a directory: (start) %%HP: T(3)A(D)F(.); DIR P1 @ ASC-> Version 1. << IF DUP TYPE 2 =/ THEN Not A String DOERR END RCWS -> ws << 16 STWS #0 NEWOB SWAP DUP SIZE IF DUP 4 < THEN DROP SWAP DROP Invalid String DOERR END DUP 65 / IP - 4 - # 18CEAh SYSEVAL OVER # 61C1Ch SYSEVAL SWAP # 6641F8000AF02DCCh # 130480679BF8CC0h # 518Ah SYSEVAL # 19610313418D7EA4h # 518Ah SYSEVAL # 7134147114103123h # 518Ah SYSEVAL # 5F6A971131607414h # 518Ah SYSEVAL # 12EA1717EA3F130Ch # 518Ah SYSEVAL # 280826B3012808F4h # 518Ah SYSEVAL # 6B7028080BEE9091h # 518Ah SYSEVAL # BE5DC1710610C512h # 518Ah SYSEVAL # 705D00003431A078h # 518Ah SYSEVAL # 3D8FA26058961431h # 518Ah SYSEVAL # 312B0514h # 518Ah SYSEVAL # 18F23h SYSEVAL DUP BYTES DROP 4 ROLL IF == THEN SWAP DROP ELSE DROP Invalid String DOERR END ws STWS >> P2 @ ASC-> Version 2. To be converted by ASC-> version 1. D9D20D29512BF81D0040D9D20E4A209000000007566074726636508813011920 140007FE30B9F060ED3071040CA1304EC3039916D9D2085230B9F06C2A201200 094E66716C696460235472796E676933A1B21300ED30FD5502C230C1C1632230 CCD20FA0008F14660CC8FB97608403104AE7D814313016913213014117414317 414706131179A6F5C031F3AE7171AE214F8082103B6280821909EEB0808207B6 215C0160171CD5EB870A13430000D50713416985062AF8D341508813044950B9 F06BBF06EFC36B9F0644230C2A201200094E66716C696460235472796E676933 A1B2130B21300373 P3 @->ASC. To be converted by ASC->. D9D20D2951881304495032230FD5502C230A752688130ADB467FE30322306AC3 0CB916E0E30CBD30F6E30C1C1632230CCD20DC0008F14660CC8FB97608403104 AE7D8143130169174147061741431311534AC6B4415141534946908D9B026155 4A6F53131F3AE731A014C161AE215F08082103A6280821939EEC08082170A621 4C161170CD56B870A18503430000D5071351796A9F8D2D02639916D9D2085230 C2A209100025F4D402F426A6563647933A1B2130A2116B213033C0 SETUP @Automatic setup program << P2 P1 'ASC->' STO P3 ASC-> '->ASC' STO { P1 P2 P3 SETUP } PURGE >> END (end) Installation instructions: 1. Edit the above text between (start) and (end) into a text file named CONV (for example). Be sure that you leave the strings exactly as entered above, with no extra spaces or other invisible characters at the beginnings or ends of the lines. 2. Set the HP 48SX into ASCII transfer mode. 3. Using Kermit, download CONV text file to the 48, verify its checksum (6C8Ah). 4. Execute CONV to make it the current directory. 5. Execute SETUP. 6. The directory CONV now contains ASC-> and ->ASC, ready to use. To archive the decoded versions of ASC-> and ->ASC back on your computer, be sure to set the HP 48SX in binary transfer mode before uploading. Disclaimers: + Use the programs at your own risk. Any time you delve into the SYSEVAL world, there are increased dangers. Archive your 48 memory before experimenting with these programs! Also, verify the checksums of objects defined above to make sure they have been downloaded correctly, before executing ASC->. + I will not answer questions about how the programs work. This is not because of any great secrecy, but rather because it's hard to give any answer that doesn't lead to more questions, and more, and more... + 48 hackers are welcome to mine any nuggets they can from the programs, and from the fact that ->ASC is a convenient way to decompile an object. ****************************************************************** * Appendix B: Using non-HP RAM cards in your HP 48SX: If you use RAM cards that are NOT designed for the HP 48SX, it is possible to severely damage your HP 48SX. If you want to be safe, you should only use RAM cards designed for the HP 48SX. Here is an edited discussion from comp.sys.handhelds. From steveh@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: steveh@hpcvra.CV.HP.COM (Steve Harper) Date: Thu, 10 May 1990 22:46:09 GMT Subject: RE: HP48SX Memory Card Pricing Organization: Hewlett-Packard Co., Corvallis, OR, USA There has been a substantial amount of comment regarding the memory cards for the HP48SX and their prices. My purpose in this response is not to attempt to justify any particular price, but rather to present the technical reasons why there is a substantial price difference between the memory cards and other types of expansion memory for PC's, for example, with which users are probably more familiar. Some users have correctly pointed out that the memory in the cards is static RAM rather than dynamic RAM commonly used in PC's. Dynamic RAM uses one transistor and a capacitor for each bit of memory whereas static RAM requires either four transistors and two resistors, or six transistors. The net result is that an equivalent amount of static RAM is much larger and therefore much more expensive than dynamic RAM. The advantage is that static RAM doesn't need to continually be running and drawing current (refresh cycles) to retain the contents of memory. In addition, the static memory used in the cards is not just any static memory, but is specially processed and/or selected for very low standby current. This allows the backup battery in the card to keep memory alive for a very long time, rather than requiring the user to replace it every few months. The special processing and/or special testing to select low current parts adds to the already higher cost of the static RAM chips. The standard molded plastic DIP package used for most integrated circuits, including memory chips, is relatively inexpensive because of its simplicity and the huge volumes. Unfortunately, these packages are too large to put into a memory card. Therefore, the card manufacturer mounts the individual silicon memory chips directly on a special thin PC board together with the memory support chips. Because multiple chips are being placed in a single hybrid package in a special process which has lower volume, yields are lower and this again causes the cost to be higher. Indeed, the yield becomes exponentially worse as the number of chips and interconnections increases in such a packaging process. In addition to the memory chips themselves, two more integrated circuits and several discrete components are required for power and logic control. A bipolar technology chip senses the external voltage and switches the power to the chips from the internal keep-alive battery as needed. A CMOS gate array chip protects the memory address and data lines from glitches/ESD when the card is not plugged in. This chip also generates the proper enabling signals when there are multiple memory chips in the card, as is presently the case with the 128 Kbyte RAM card. These chips must be designed for extremely low current, just as the memory chips are. In addition to the battery and the battery holder, the other mechanical parts are important, too. The molded plastic frame holds the PC board and provides the foundation for the metal overlays and the shutter-and-springs assembly which protects the contacts from ESD and from contaminants. The write-protect switch is also an important feature. It is quite expensive for the manufacturer to make the tools necessary to fabricate each of these parts as well as the tools to assemble and test the complete card. While the volume of memory cards is relatively low this tooling cost represents a significant part of the cost of each card. Admittedly, there are other alternatives, such as those presently used in PC's, to provide a memory expansion capability. To provide that kind of expansion would require the calculator to be much larger than it is and possibly more expensive. This is clearly very undesirable. Other features that were felt to be essential were the ability to distribute software applications and to share and archive/backup user-created programs and data. Other expansion alternatives do not provide these important benefits. The IO capabilities of the calculator provide these features only to a limited degree. One other item bears repeating here: Memory cards for use in the calculator will clearly indicate that they are for use with the HP48SX. Other memory cards exist which are mechanically compatible with the HP48S, but these cards cannot be relied upon to work electrically in the calculator. The HP48SX cards are designed for a lower supply voltage range. Use of the other cards may cause memory loss, and under certain circumstances may even damage your calculator electrically. From steveh@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: steveh@hpcvra.CV.HP.COM (Steve Harper) Date: Fri, 11 May 1990 16:52:07 GMT Subject: Re: Memory Card: Give Us *True* Facts! Organization: Hewlett-Packard Co., Corvallis, OR, USA My previous statement that under certain circumstances the calculator may even be damaged electrically is not a ploy. If the calculator's internal power supply voltage happens to be near the low end of the range, say 4.1 V, and the voltage at which the card's voltage control chip shuts it down happens to be near the high end of its range, say 4.2 V (this can and does occasionally occur for the non-HP48SX cards), then the calculator will start to drive the memory address lines and the card will still have these clamped to ground (that's what it does to protect itself when there is not sufficient system voltage to run). This unfortunate situation may simply trash your memory, or if the calculator tries to drive enough of the lines high at the same time, several hundred milliamps may flow...for awhile that is, until something gives up... On the other hand, your calculator and a particular non-HP48SX card may work just fine if those voltages happen to be at the other end of their ranges. These voltages are also slightly temperature sensitive. It may work in the classroom or office and not at the beach, or vice versa. The voltage trip point of the HP48SX cards has been set lower (a different voltage control chip) so that this cannot occur, regardless of part and temperature variations. One other item was brought to my attention yesterday by Preston Brown that I should have included in my original posting here. While most of us recognize that comparing ram cards to a handful of dynamic ram chips to plug into your PC is apples and oranges, it may be more interesting to compare the HP48SX cards with cards for other products, like the Atari Portfolio, the Poquet, the NEC Ultralite, etc. I believe you will find that the prices on the HP48SX cards are not at all out of line. Steve I claim all disclaimers... the non-HP48SX cards From prestonb@hpcvra.CV.HP.COM Fri Mar 1 17:00:00 1991 From: prestonb@hpcvra.CV.HP.COM (Preston Brown) Date: Thu, 17 May 1990 17:26:53 GMT Subject: Re: Memory Card: Give Us *True* Facts! Organization: Hewlett-Packard Co., Corvallis, OR, USA When the RAM cards detect that voltage is to low to operate they clamp the address lines to ground. This clamping is done by turning on the output drivers of a custom chip included on the card. The clamping current is speced at 2mA min at the Vol output level. Since the 48 can be trying to drive the line all the way high even more current is typical. 10mA per fight is not uncommon with totals of several hundred mAs. The VDD power supply is regulated at 4.1 - 4.9 with typical parts at the low end (4.3). The power to the cards is switched thru a transistor, creating up to a 0.1V drop. Standard Epson cards have a significant chance of seeing this voltage as to low and shutting down. We have seen cards do this in the lab. When it occurs the calculator locks up with VDD pulled down to about 2.5V and 250mA being drawn from the batteries. This current drain greatly exceeds the ratings for the power supply and can damage your calc. The least that will happen is a loss of memory. Now, why didn't we regulate VDD higher? The 48 has two power supplies VDD at 4.3 and VH at 8.5. VH cannot be regulated higher without exceeding the spec for our CMOS IC process. VH is used as the + voltage for the I/O. In order to meet a +3V output level VH must be more then 3.6V above VDD. (VDD is used as I/O ground). Our power supply system increase the battery life and reduces the cost greatly for the wired I/O. Preston ****************************************************************** * Appendix C: What's new in the HP 48G/GX? [ The following was taken from a posting by Joe Horn. ] +--------------------+ | WHAT'S NEW | | IN THE HP48 G/GX | +--------------------+ collected & annotated by Joseph K. Horn (1) AUTOMATIC LIST PROCESSING. Almost all commands that did not accept a list as one of their arguments can do so now. Here are just a few examples: { 1 2 3 } SF sets flags 1, 2, and 3 { 1 2 3 } SQ returns { 1 4 9 } { 1 2 3 } { 4 5 6 } * returns { 4 10 18 } { freq dur freq dur ... } BEEP can play a song with no audible hiccup between tones. Since + has always been used to concatenate lists, a new ADD function exists to add the elements of two lists, like this: { 1 2 3 } { 4 5 6 } ADD returns { 5 7 9 }, whereas { 1 2 3 } { 4 5 6 } + returns { 1 2 3 4 5 6 } as it did before. (2) PORTS. Only port 1 can be merged in the GX. Card slot 2, which is intended for large-capacity RAM cards, is permanently free, and is automatically divided up into 128K ports, each of which becomes Port 2, Port 3, Port 4, etc. Up to 4 Megabytes can be plugged into slot 2, which would then become Port 2 through Port 33. (Although the FREE and MERGE commands were kept for HP 48SX compatibility, GX users will prefer the new FREE1 and MERGE1 commands). Therefore the maximum amount of merged main memory is 256K (unlike the SX which allowed up to 288K) after MERGE1; the maximum amount of fully online free independent memory is 4224K after FREE1. (3) LOCAL VARIABLES. Variable names prefixed with a <- (backarrow character) are compiled as local (temporary) variable name objects even if they're not explicitly after FOR or ->. This allows programs to share values through local variables, which is much faster than sharing values through global variables, and they get purged automatically. (4) SPEED. CPU clock speed is double the S/SX's, but throughput is estimated to be only 40% faster, primarily due to the fact that *all* RAM & ROM is now bankswitched (on the S/SX only a 32K portion of the ROM required bank switching), and it still has the same 4-bit bus bottleneck. (5) IMPROVED COMMANDS: AXES can now also specify the spacing of the tick marks. DEPND can now also specify the initial values and tolerance for the new DIFFEQ plot type. (6) HP SOLVE EQUATION LIBRARY CARD COMMANDS: AMORT, amortization calculations CONLIB, starts Constants Library catalog CONST, returns value of a named CONLIB constant DARCY, calculates Darcy friction factor EQNLIB, starts Equation Library catalog F0lambda, calculates black-body power fraction FANNING, calculates Fanning friction factor MCALC, marks an MSOLVR variable as not user-defined MINEHUNT, starts the Minehunt video game MINIT, initializes Mpar from 'EQ' for MSOLVR MITM, customizes title & menu of MSOLVR's screen MROOT, solve for variable(s) in MSOLVR MSOLVR, shows Multiple Equation Solver menu MUSER, marks an MSOLVR variable as user-defined SIDENS, density of silicon as function of temperature SOLVEQN, starts solver for specified EqLib equation(s) TDELTA, subtracts temperatures like - ought to but doesn't TINC, adds temperatures like + ought to but doesn't TVM, shows the financial calculator (Time Value of Money) menu TVMBEG, sets payments-at-beginning-of-periods mode TVMEND, sets payments-at-end-of-periods mode TVMROOT, solves for a TVM variable ZFACTOR, calculates gas compressibility factor Z Note: The EQ Card's Periodic Table and Tetris game are *not* in the HP 48G/GX. (7) NEW ARRAY COMMANDS: COL+, inserts a column vector into a matrix or a number into a vector (like INSCOL/PUTCOL in Donnelly's Tool Library) COL-, deletes a column from a matrix or number from a vector (identical to DELCOL in Donnelly's Tool Library) COL->, combines multiple column vectors into a matrix ->COL, breaks a matrix into multiple column vectors (like repeated GETCOL in Donnelly's Tool Library) COND, column norm condition number of a square matrix CSWP, swaps two columns in a matrix (like EXCOL in Donnelly's Tool Library) ->DIAG, returns vector of major diagonal elements of a matrix DIAG->, creates matrix with specified diagonal elements EGV, eigenvalues and right eigenvectors of a square matrix EGVL, eigenvalues of a square matrix FFT, discrete Fourier transform IFFT, inverse discrete Fourier transform LQ, returns the LQ factorization of a matrix LSQ, minimum norm least-squares solution to an ill-determined system of linear equations LU, returns the Crout LU decomposition of a square matrix PCOEF, returns polynomial with given roots (inverse of PROOT) PEVAL, evaluates polynomial at x PROOT, finds all roots of polynomial (inverse of PCOEF) QR, returns QR factorization of a matrix RANK, rank of a rectangular matrix (uses flag -54) RANM, creates matrix with random elements RCI, multiplies elements in one row of a matrix by a scalar RCIJ, does RCI then adds the result to a row ROW+, inserts a row vector into a matrix or a number into a vector (like INSROW/PUTROW in Donnelly's Tool Library) ROW-, deletes a row from a matrix or number from a vector (identical to DELROW in Donnelly's Tool Library) ROW->, combines multiple row vectors into a matrix ->ROW, breaks a matrix into multiple row vectors (like repeated GETROW in Donnelly's Tool Library) RSWP, swaps two rows in a matrix (identical to EXROW in Donnelly's Tool Library) SCHUR, computes the Schur decomposition of a square matrix SNRM, spectral norm of an array SRAD, spectral radius of a square matrix SVD, singular value decomposition of a matrix SVL, computes the singular values of a matrix TRACE, sum of diagonal elements of a square matrix (8) GRAPHICS & PLOTTING COMMANDS: ANIMATE, displays grobs on the stack sequentially. You can use the defaults, or specify your own delay between frames (can be *very* fast), the number of times to repeat the sequence, and even the pixel coordinates. It's just like a ROLL REPL loop... except very fast. Note: Charlie Patton converted 17 seconds of the Apollo moon-walk video into HP48 GROBs and ran them with ANIMATE, and it looked very good! ATICK, specifies tick spacing on plot axes EYEPT, specifies the eye-point coordinates in a perspective plot GRIDMAP, selects the new gridmap plot type PARSURFACE, selects the new parametric surface plot type PCONTOUR, selects the new pcontour plot type PICTURE, same as GRAPH command SLOPEFIELD, selects the new slopefield plot type WIREFRAME, selects the new wireframe plot type XVOL, sets the width of the 3D plotting volume XXRNG, sets the width of the 3D target mapping range for gridmap and parametric surface plots YSLICE, selects the new yslice plot type YVOL, sets the depth of the 3D plotting volume YYRNG, sets the depth of the 3D target mapping range for gridmap and parametric surface plots ZVOL, sets the height of the 3D plotting volume (9) USER-INTERFACE COMMANDS: CHOOSE, displays a point-and-click menu dialog box INFORM, formatted multi-line input with named fields (nice!!) MSGBOX, displays text in a centered box with shadow, then WAITs NOVAL, placeholder for unspecified values in INFORM argument list (10) LIST PROCESSING COMMANDS: ADD, adds lists element-wise (see section #1 above) DOLIST, evals an object on multiple lists DOSUBS, evals a program or command taking arguments from a list ENDSUBS, returns the number of loops the current DOSUBS will do HEAD, first element in a list or first char in a string (identical to CAR in Donnelly's Tool Library) DeltaLIST, list of first finite differences of list objects SigmaLIST, sum of the elements in a list PiLIST, product of the elements in a list NSUB, returns the current list pointer value during a DOSUBS REVLIST, reverses the order of the objects in a list (like REVERSE in Donnelly's Tool Library) SEQ, list of results from repeated execution of an object (like a FOR/STEP loop but the results go into a list) SORT, sorts elements in a list into ascending order, or sorts a list of lists using each list's first element as the key (can be done with LSORT/QSORT in Donnelly's Tool Library) STREAM, executes an object on first two elements of a list, then again on the result and the 3rd element, etc. Allows easy creation of things similar to SigmaLIST and PiList. TAIL, returns a decapitated list or string (see HEAD above) (identical to CDR in Donnelly's Tool Library) (11) SYSTEM COMMANDS: CYLIN, sets polar/cylindrical coordinate mode FREE1, like 1 FREE (see section #2 above) MERGE1, like 1 MERGE (see section #2 above) PINIT, port initialize, esp. important for 4-Meg RAM card users RECT, sets rectangular coordinate mode SPHERE, sets polar/spherical coordinate mode TEACH, loads the Owner's Manual examples into a dir in HOME VERSION, returns the operating system ROM version string Note: first 48G's will be version K; first 48GX's will be version L due to the removal of a port management bug in version K which does not affect the 48G. XRECV, Xmodem protocol receive (binary mode only) XSEND, Xmodem protocol send (binary mode only) (11) MATH COMMANDS: LININ, tests whether an equation is linear in a given variable NDIST, normal probability density PCOV, population covariance of SigmaDAT PSDEV, population standard deviation of SigmaDAT PVAR, population variance of SigmaDAT RKF, solves initial value problem using Runge-Kutta-Fehlberg RKFERR, change in solution and absolute error using RKF RKFSTEP, next solution step with given error tolerance using RKF RRK, solves initial value problem using Rosenbrock & RKF RRKSTEP, next solution step with given error tolerance using RRK RSBERR, change in solution and absolute error using Rosenbrock (12) MENU NUMBERS & KEY CODES. Many menu numbers have changed, so software that uses # MENU or # TMENU may not work the same as in the HP 48S/SX. (Specifically, only menu numbers 0-3, 28, 30, and 42-59 are the same). Likewise, almost all of the shifted keycodes correspond to new commands and menus, which programmers must take into account; for example, the RAD key on the S/SX had the keycode 82.2, but it's 21.2 on the G/GX. The left-shift key, which was orange on the S/SX, is now purple [officially lavender], and the right-shift key which was blue on the S/SX is now green [officially teal] on the G/GX. Also, the digit-key menus can be activated by both shift keys; left-shift gives the softkey menus like in the S/SX, but the right-shift gives the new user-friendly full-screen menus. The unshifted keys remain identical to the S/SX, except for a cosmetic color change to match the very dark green of the calculator case. (14) MANUALS. The G/GX comes with two manuals, a Getting Started manual for newbies, and a cost-cutting, slimmer owner's manual called the User's Guide which will *not* cover programming in depth, since HP figures that the huge majority of all 48 owners never program it anyway. The few power users (namely, us!) can buy the optional Advanced Users Guide (similar to the S/SX's Programmer's Reference Manual) which covers programming and other topics. Note: The accuracy and completeness of this list is in no way guaranteed, but I included everything I could find and tried to make it all clear. Please post addenda & corrigenda as you discover them so that we S/SX owners can all make a fast transition to the G/GX. ******************************************************************* * Appendix D: The EquationWriter Bug & Rev J Bugfix [ The following was taken from a posting by Joe Horn. ] Rev A-E EquationWriter Bug & Rev J Bugfix ----------------------------------------- observed by Joe Horn +------------------+ | Rev E behavior | +------------------+ Clear flag -53 first (the Precedence Flag). On a Rev E, put '((1+2)/(3+4))^5' on the stack and press down-arrow. You'll see: 5 / 1+2 | --- | (A) 3+4 / which is as it should be. But now press [orange-shift] [+]; see the message Implicit () off momentarily; press [left-arrow] (not backspace), then press the [EXIT] softkey. The expression gets mangled into this: 1+2 ----------- (B) (5) (3+4) which is not equal to expression (A) above! Bug, yes? Press [ON] to abort the process. Now set flag -53, then repeat the above procedure. First you see: 5 / 1+2 | --- | (C) 3+4 / which is the same as (A) above; but continuing as before, you see: (5) / 1+2 | ----- | (D) (3+4) / which *is* equal to the original. Thus the bug can be worked around by keeping flag -53 set (not a pleasant solution). +------------------+ | Rev J behavior | +------------------+ Major difference: after pressing down-arrow, Rev J goes directly into graphic mode, so you have to press ON and then EXIT to get into the equation editor (which Rev E goes directly into). But that's petty cash compared to the following big change. The same sequence of operations, first with flag -53 clear, then set, exactly as detailed above, yields these four displays in a Rev J: 5 / (1+2) | ----- | (A') 3+4 / (notice the extra parentheses?) and then: 5 / (1+2) | ----- | (B') (3+4) / which *is* equal to (A'); nothing at all like expression (B) above! and then: 5 / (1+2) | ----- | (C') 3+4 / which is the same as (A') above; and then: 5 / (1+2) | ----- | (D') (3+4) / which is also equal to (A'). No bug in Rev J. SUMMARY: Rev A-E have a bug in the EquationWriter that can mangle expressions if flag -53 is clear (the default) and if Explicit Parentheses mode is toggled. This bug has been fixed in Rev J. Unfortunately (as you can see above) Rev J *always* puts parentheses around polynomial numerators. It is therefore impossible to use the ->GROB command on a Rev J to create a GROB that looks like expression (A) above; the simplest that can be had is expression (A'). Another minor change, while I'm at it: Rev A-E don't change the menu when you press REPL; Rev J automatically flips to the appropriate RULES menu. None of these changes are documented anyplace that I'm aware of. Please post any corrections & additions you find. Thanx. -Joseph K. Horn- -Peripheral Vision, Ltd.- akcs.joehorn@hpcvbbs.cv.hp.com Disclaimer: I don't work for HP, EduCALC, or anybody else. ****************************************************************** * Appendix E: Compact Data Storage: From Jim Donnelly (jimd@cv.hp.com): A simple length-encoding technique can be put to use for a free-format, very compact multi-field data storage system. Two tiny programs, SUBNUM and STRCON are here to help the process, and are listed near the end of this note. At the end of the note is a directory that may be downloaded into the HP 48 that contains the examples. The principle is to store starting indices in the beginning of a string that point to fields stored subsequently in the string. The indices are stored in field order, with an additional index at the end to accommodate the last field. There are several small points worth mentioning: 1) Fields may be 0-length using this technique. 2) The execution time is uniform across all fields. 3) This technique saves about 4 bytes per field after the first field, because the string prolog and length are omitted for fields 2 -> n. EXAMPLE: -------- Indices | Fields Character | 1 11111111 12222222222 Position : 1 2 3 4 |567890 12345678 90123456789 +--+--+--+--+------+--------+-----------+ String : | 5|11|19|30|Field1| Field2 | Field 3 | +--+--+--+--+------+--------+-----------+ This is a string that contains 3 fields, and therefore 4 index entries. The first field begins at character 5, the second field begins at character 11, and the third field begins at character 19. To keep the pattern consistent, notice that the index for field 4 is 30, which is one more than the length of the 29 character data string. To extract the second field, place the string on the stack, use SUBNUM on character 2 to extract the starting position, use SUBNUM on character 3 to extract the (ending position +1), subtract 1 from the (ending position+1), then do a SUB to get the field data. NOTE: The index for field 1 is stored as character code 5, NOT 5! To place the field index for field 1 in the string, you would execute data 1 5 CHR REPL. PROGRAM: -------- The following program accepts an encoded data string in level 2 and a field number in level 1: DECODE data field# --> field << --> f << DUP f SUBNUM ; data start --> OVER f 1 + SUBNUM ; data start end+1 --> 1 - ; data start end --> SUB ; field --> >> >> DATA ENCODING ------------- The following program expects a series of 'n' strings on the stack and encodes them into a data string suitable for reading by the first example above. The programs SUBNUM and STRCON are used to assemble the indices. ENCODE field n ... field 1 n --> data << DUP 2 + DUP 1 - STRCON --> n data << 1 n FOR i data i SUBNUM OVER SIZE ; ... field index fieldsize + data SWAP ; ... field data index' i 1 + i + SWAP CHR REPL ; ... field data' SWAP + 'data' STO ; ... NEXT data ; data >> >> In this example, four strings are encoded: Input: 5: String 4: Str 3: STR 2: STRING 1: 4 Output: xxxxxSTRINGSTRStrString (23 character string) (The first five characters have codes 6, 12, 15, 18, and 24) VARIATION: ---------- The technique above has a practical limit of storing up to 254 characters of data in a string. To overcome this, just allocate two bytes for each field position. The code to extract the starting index for becomes a little more busy. In this case, the index is stored as two characters in hex. Indices | Fields Character | 11111 11111222 22222223333 Position : 12 34 56 78|901234 56789012 34567890123 +--+--+--+--+------+--------+-----------+ String : |09|0F|17|21|Field1| Field2 | Field 3 | +--+--+--+--+------+--------+-----------+ << --> f << DUP f 2 * 1 - ; data data indx1 --> SUBNUM 16 * ; data 16*start_left_byte --> OVER f 2 * SUBNUM + ; data start OVER f 2 * 1 + SUBNUM ; data start end_left_byte --> 16 * 3PICK f 1 + 2 * SUBNUM + 1 - ; data start end --> SUB ; field --> >> >> TWO VERY TINY HELPFUL PROGRAMS ------------------------------ SUBNUM string position --> code << DUP SUB NUM >> STRCON code count --> repeated string << --> code count << code CHR 'code' STO 1 count START code + NEXT >> >> A DIRECTORY YOU CAN DOWNLOAD ---------------------------- This is a directory object. Cut after the === to the end of the file and download to your HP 48 using the ASCII transfer. ======================================================================== %%HP: T(3)A(D)F(.); DIR DECODE << -> f << DUP f SUBNUM OVER f 1 + SUBNUM 1 - SUB >> >> ENCODE << DUP 2 + DUP 1 - STRCON -> n data << 1 n FOR i data i SUBNUM OVER SIZE + data SWAP i 1 + SWAP CHR REPL SWAP + 'data' STO NEXT data >> >> STRCON << -> code count << code CHR 'code' STO 1 count START code + NEXT >> >> SUBNUM << DUP SUB NUM >> END ****************************************************************** * Appendix F: Various useful functions Begin OBJFIX.DOC ----------------------------------------------------------------------- OBJFIX by HP for SX and GX When a binary object received by Kermit on the HP-48 is left as a string beginning with HPHP48, OBJFIX will extract the HP-48 object if the only problem is that extra bytes got appended to the end. OBJFIX takes a variable name in stack level 1 and modifies the contents of the variable if no other problems are detected. [Note: This is like FIXIT by Horn & Heiskanen on Goodies Disk #8, but this one is by HP and so I suppose it's more reliable. Although it fails the test cases included with FIXIT, that may be because they were artifically contrived cases. Try both on real-world downloads that need fixing. Which do you like better? -jkh-] ----------------------------------------------------------------------- End OBJFIX.DOC --------Cut-Between-the-Lines:-Begin-OBJFIX.ASC----------------------- %%HP: T(3)A(D)F(.); D9D202BA81D9F81B2040D9D20F2A26DA91629C8145126489162C23072C80CCD2 0BD0008FB9760147108134164142C2818F24D534501008B2F41643150D73B840 58405438314A161966D2BF6BF6A6F5BE16314213114334CF8208A6F58F235A04 55136D7D4EA494D231A1CA101110131CA130DBE284F8FC0760D41198F29960D4 130142119EA1408F5E0108D341503223072D70B2130B21301460 --------Cut-Between-the-Lines:-End-OBJFIX.ASC------------------------- Begin FIXIT.DOC ----------------------------------------------------------------------- (Comp.sources.hp48) Item: 139 by akcs.joehorn@hpcvbbs.cv.hp.com [Joseph K. Horn] and mheiskan@hut.fi [Mika Heiskanen] Subj: Fixit v3.2, repairs bad downloads Date: 14 Jul 1992 PURPOSE: ------- Converts a badly uploaded string into the original object. THEORY: ------ A lot of folks upload HP 48 objects poorly, such that when you download them, you just get strings full of garbage that look something like this: HPHP48-E#c&r$a%p@!*!... [looks familiar, eh?] That's because they uploaded it using XMODEM, or managed to screw it up some other way. The following FIXIT program takes such a string and extracts the actual HP 48 object that they originally intended to upload (if at all possible). Such object extraction can be done by hand, but it's too dangerous. FIXIT minimizes the danger of Memory Clear. It checks whether the extracted object is a valid one, and if not, drops it from the stack before the HP 48 attempts to display it. All of the many bad downloads I've archived over the years are fixed by FIXIT, whereas about half of them cause a Memory Clear when extracted manually. No guarantees, however. Use at your own risk. The actual extraction is done by a Code object written by Mika Heiskanen. The User RPL shell around this code object is what minimizes the danger of Memory Clear; it was written by Joe Horn. INSTRUCTIONS: ------------ BACKUP YOUR MEMORY, just in case the string contains a logic bomb. Place the bad download on the stack (see HPHP48-...) and run FIXIT. Possible results: (1) No error: the object was extracted successfully and is on level 1. (2) Bad Argument Type error: you didn't have a string on level 1. (3) Bad Argument Value error: the string wasn't of the proper form; it must be an HPHP48-... downloaded string. (4) Invalid Definition error: the object was mangled in transmission so badly that its end was lost; the object cannot be extracted. (5) Undefined Result error: there is no HP 48 object in the string. (6) Recover Memory? YES/NO: the string contained a bomb, and FIXIT detonated it. Press YES to sift through the shrapnel and rubble in a feeble attempt to resurrect the dead. Press NO to bury them. EXAMPLES: -------- To do the following examples, download the FIXIT directory to your HP 48 and get into it. (1) Press HI. See HPHP48-E%$@#%@..., a badly uploaded download. Before pressing FIXIT to fix it, try doing what we all used to do: press EDIT to see if we can recognize anything (usually a futile attempt). We see: HPHP48-E%@$#%$@... << Melancholy Baby >> But looks can be deceiving; press ON to exit the editor, and then press FIXIT to extract the intended upload: << Happy Camper >> (2) Press WTAV; see another garbage download. But EDIT refuses; the string contains nulls. Press FIXIT; see successfully extracted directory. (3) Press BAD1. Notice that it looks exactly like WTAV. (Press WTAV, compare, then DROP). But its ending is all messed up; manually extracting WTAV from BAD1 can cause Memory Clear. Press FIXIT and see Error: Invalid Definition indicating that the object inside BAD1 is so mangled that its end cannot be located. (4) Press BAD2. Looks like WTAV again. But its body is messed up; manually extracting it would create an External object that could cause Memory Clear if evaluated. Press FIXIT and see Error: Undefined Result indicating that there is nothing recognizable inside BAD2. ----------------------------------------------------------------------- End FIXIT.DOC --------Cut-Between-the-Lines:-Begin-FIXIT.ASC------------------------ %%HP: T(3)A(D)F(.); 69A20FF7CE20000000402414442340C2A203B000840584054383D25403A20FF7 2500000000403535947440D9D20E16329C2A2DBBF13013216DF1406A1C42328D BF193632B213034000407545146540D9D20E163292CF1EFFB1DBBF1EBFB150FA 193632B2130003030303034C000402414441340C2A203B000840584054383D25 469A20FF72500000000403535947440D9D20E16329C2A2DBBF13013216DF1406 A1C42328DBF193632B213034000407545146540D9D20E163292CF1EFFB1DBBF1 EBFB150FA193632B2131313131313134C000407545146540C2A203B000840584 054383D25469A20FF72500000000403535947440D9D20E16329C2A2DBBF13013 216DF1406A1C42328DBF193632B213034000407545146540D9D20E163292CF1E FFB1DBBF1EBFB150FA193632B2130003030303034C00020849420C2A20570008 40584054383D254D9D20E163284E2050841607079784E20603416D6075627936 32B2130A0BA02D456C616E63686F6C697022416269702BB28000506494859445 50D9D20E16323CE2278BF168BC1ED2A2167E1AFE22D9D203CE2278BF19C2A274 3A2C58C1C2A2031000840584054383D2167E1AFE22D9D2078BF18B9C1DBBF1AA F028DBF1CCD201200014713717917F137145142164808C5BF22D9D2033920200 0000000005150933A1B21305DF22B21305BF22D9D20339202000000000004150 933A1B21305DF223CE2278BF168BC1D8DC1167E1AFE22D9D203FBF1339202000 000000002770933A1B21305DF223CE2278BF19D1A1DBBF18DBF1E0CF1D5CE1AF E22D9D208DBF1339202000000000000030933A1B21305DF22CB2A193632B2130 B21303D4F --------Cut-Between-the-Lines:-End-FIXIT.ASC-------------------------- ******************************************************************* (Shamelessly lifted from the HP-41C manual:) The LASTX function is useful in calculations where a number occurs more than once. By recovering a number using LASTX, you do not have to key that number into the calculator again. For example, calculate: 96.704 + 52.394706 -------------------- 52.394706 Keystrokes: Stack: ------------------ -------------------- 96.704 ENTER 96.704 52.304706 + 149.098706 LASTX 149.098706 52.304706 / 2.84568265351 @ @ This is a version of LASTX for the HP 48 @ %%HP: T(3)A(D)F(.); << DEPTH -> n << LASTARG DEPTH n - DUP -> s << ROLLD s 1 - DROPN >> >> ****************************************************************** * Appendix G: Rotation rate to angular frequency conversion bug [Editor's Note: A counter point to this bug report is provided at the end appendix] By: Wlodek Mier-Jedrzejowicz wlodek@ic.ac.uk (or if that fails, try wacm@doc.ic.ac.uk) Posted to comp.sys.hp48 on April 29, 1994 ----BEGIN QUOTED MATERIAL----------- ROTATION RATE TO ANGULAR FREQUENCY CONVERSION BUG There is a rotation rate conversion bug in the HP48G/GX which I have not seen reported here before, so after discussion with the folks at Corvallis I am posting this description. Warning: it is 159 lines long! First - an example. Put the unit object 60_rpm in level 2 and the unit object 1_r/s in level 1, then execute the command CONVERT. You are asking the HP48 to convert a rotation rate of 60 revolutions per minute into an angular frequency in radians per second. 60 rpm is 1 revolution per second, or 2pi radians per second. No HP48G/GX will give this answer! Not everyone uses rpm or is even aware of the existence of this unit - it is one of the extra units in the UTILS menu of the Equation Library - so here is a second example - add 2pi radians per second to one Hertz. Put 6.2832_r/s in level 1, 1_Hz in level 1, and add. You are adding an angular frequency of two pi (one cycle) per second to a rotation rate of one per second, so the result should be a frequency of two Hertz. On an HP48S/SX that is the answer. On an HP48G/GX it is not. When units are converted, by CONVERT, or during arithmetic on unit objects, the level 2 object is first turned into base units, and then the result is converted into the units of the level 1 object. On the HP48S/SX, the base unit of angles is one rotation (or a unit circle or a revolution or a cycle). So, the angle unit of rpm (a revolution) or of Hz (a cycle if Hz is treated as a rotation rate) is already in base units - conversions to angles involving rpm and Hz automatically work correctly. On the HP48G/GX, the base unit of angles is the current angle mode (DEG, RAD or GRAD) - so any conversion from rpm or Hz (or any formula which works in cycles, rotations, revolutions, unit circles) to angles should be preceded by a conversion from the unit circle to the current angle. Apparently no-one noticed this would be necessary, because it all worked automatically on the HP48S/SX. So, when you convert 60_rpm to units of _r/s, an HP48G/GX converts not 60 rotations but 60 base angle units per minute to radians/second. In RAD mode, you get 1 radian per second. In DEG mode you get 1 degree per second, and in GRAD mode you get 1 grad per second (in each case expressed in radians). That's three different answers, none of which is correct! Exactly the same happens if you convert 1_Hz to angles per second, and the inverse mistake is made if you convert angles per time to cycles or rotations divided by time. I first learned of this bug from a member of HPCC (the British club for users of HP handhelds), Peter Embrey. He describes his troubles in articles in the first two 1994 issues of our club journal, DATAFILE (in Volume 13 number 1 pages 12 to 14 and V13n2p6). He was calculating the energy stored by a flywheel - given by the formula (1/2)*I*omega^2 and after a time he decided the answers had to be much too big when he CONVERTed from kg*m^2*(r/s)^2 to W*h on an HP48GX. It turns out that (r/s) are the correct units to get the right answer, but the GX was converting to degrees per second as it was in DEG mode, so his answer was too large by a factor of (360/2pi)^2 - a factor of about 3,300. In this case, his HP48SX was not much better, since it converted from radians to unit circles. The way to get the correct answer is to use an HP48G or GX in RAD mode - or to divide out the radians from the formula before using CONVERT. This is not yet a bug, but needs as much care as does use of temperature units on the HP48. But when Peter tried to deal with the problem by working in rpm, he came upon the bug described above. My thanks to Peter for putting me on the trail! Apparently this bug not been reported before - at least my friends in HP tell me that it was not on their list of known problems until I told them of it. (This means it is not fixed in the new revision R.) Why not - does everyone know about it and work around it without thinking to tell anyone else? Or does no-one use their HP48 to do calculations on rotating bodies - or do most people do calculations with rotating bodies in such a way that they do not encounter this problem? Could there be hundreds of students and engineers out there calculating and designing things on their HP48G/GX and getting wildly inaccurate results? Has anyone built a disk drive or a jet engine which rotates far too fast and will disintegrate because of this? No, of course not, all engineers know that any design calculation absolutely must be repeated on two entirely separate calculators or computer programs! :-| Maybe some students have lost marks in exams because of this though - but please, this is not intended to restart the discussion as to whether calculators should be allowed in exams! I want to underline again that apparently no-one has reported this before - which must mean that few people have been affected by it. It is therefore not a good reason to throw away your HP48G/GX or get on a high horse and demand that HP replace your HP48G/GX - but I think it is important that people be warned so they can take appropriate avoiding action. The rest of this message goes into more detail - if you never worry about rotation calculations then you can safely ignore the rest - though you might find it interesting, so don't stop yet :-) One way to avoid this would be to add a new unit to the HP48 - call it what you like - the cycle or rotation or revolution or unit circle. As I wrote above, this is already implied in the HP48S/SX; to see this on an HP48S/SX, put 360 degrees in level 1 and execute UBASE - the result is 1, meaning that 360 degrees are equivalent to one base unit of angle measurement, but that there is no named HP48 unit corresponding to this. In contrast, UBASE on an HP48G/GX considers the base unit of angle measurement to be the radian, even though CONVERT behaves as though the base unit is the current angle mode. There appear to be two different norms for base angle units on the HP48G/GX! The whole subject gets very little mention in HP's manuals. In the original HP48SX manual (two volumes, spiral bound), the section on Dimensionless Units of Angle in chapter 13, on page 198, warns the reader about the danger of using dimensionless units and states how angle units and scalars are treated. In the later HP48S and HP48SX manual (one volume), the same warning is given in Converting Dimensionless Units of Angle, on page 13-12. The HP48G Series User's Manual, in Converting Angular Units on page 10-7, says that conversion will interpret a scalar according to the current angle mode setting. (A scalar is a pure number with no units.) For a detailed description, look in the HP48S/SX edition of HP48 Insights Vol II, section 21.4.3. This book is written by Dr Bill Wickes, who was the design team leader of the HP48SX, and who wrote the Insights books largely to provide the sort of explanations and details that get left out of manuals. A good explanation of angle units is exactly the sort of thing one can find there! He explains the pitfalls and unavoidable contradictions of working with angles in the HP48 units system and points out that the HP48S/SX make the somewhat arbitrary choice of using 2pi as the base unit of angles, thereby making conversions between angles per time and Hertz work correctly. Maybe no-one on the HP48G/GX team read this while they were making changes from the HP48S/SX! Why did they change the base unit at all? Most likely they were trying to deal with another contradiction: the units system lets you add pure numbers to angles, since both are dimensionless. If you add the number 1 in level 2 to the unit object 0_r in level 1 on an HP48S/SX, the number 1 is treated as 1 base unit, or 2pi radians, and the result is 6.2832_r - but if you take the SIN of the number 1 instead, it is not treated as 2pi, but as 1 unit of the current angle mode. The change made on the HP48G/GX does resolve this contradiction, but at the cost of introducing the bug described above. As mentioned, a way to resolve the problems involved would be to add the angle unit cycle explicitly to the HP48 units system. Hz would then be treated as cycles per second when used in calculations involving rotations - rpm would be treated as cycles per minute, and conversions would go from cycles to the appropriate angle units. This suggestion was made by Peter Embrey in his articles, and the folks at HP accept that this is a good solution - but they have not implemented it yet. In the meantime, be very, very careful when converting between units of rotation rate and units of angular frequency. I would urge everyone who does not yet have a copy of Insights II to buy one and read the relevant section - maybe that will even entice Bill Wickes into publishing his long-awaited HP48G/GX version of the book! I have not yet mentioned solid angles. In principle there should be no problem - on both the HP48S/SX and the HP48G/GX the base unit of solid angle is a unit sphere, or 4pi steradians. On the HP48S/SX you can add the pure number 1 to 0_sr and get 12.5664_sr (4pi steradians). The HP48G/GX manuals imply that exactly the same should happen, but on my (version L) HP48GX this gives the error message Inconsistent Units. This is yet another undocumented difference between the Series S and Series G but at least it is no bug! Apologies for making this description so long, I hope most people will agree that a subject like this deserves a careful description! For my next trick - some details on the HP48 Random Number Generator. ----END QUOTED MATERIAL----------- Additional insight from Eric Haas (ERICHAAS@delphi.com) The angular conversion bug is actually in the definition of the rpm unit. If you put 1_rpm on the stack, and type UBASE, you get 1.66666666667E-2_1/s. Notice that there is no angular unit in the definition. If the rpm unit is instead defined as 6_=F8/s, all conversions to and from rpms will work just fine. As an easy work-around, define the unit RPM as 6_=F8/s and use that instead of the built-in unit. If desired, one could also define the unit HZ as 60_rpm or 360_=F8/s. However, as Hz is sometimes used to describe things other than rotation rates, such a definition would not be appropriate for all circumstances. ****************************************************************** * Appendix H: How to make a Serial Cable for your HP48 From: prompt@xs4all.nl (Frank A. Vorstenbosch) HOW TO MAKE A SERIAL CABLE FOR YOUR HP48 ======================================== THE CONNECTOR FOR YOUR HP48 The connector used in your HP48 is a 4 pin (i.e. male) connector, with pins spaced 2 mm (NOT 0.1) apart. These connectors are not readily available in stores so you'll have to improvise. If you happen to have a broken floppy drive or harddisk lying around, look inside and see if you can find a connector there that will fit the HP48. Do not use a 0.1 connector, as this will damage the pins in your calculator. If you can't find a usable connector, then you'll have to make one yourself. For this you need four pins taken from a wire-wrap IC socket (available from Radio Shack or some other shop catering for DIY electronics). The smallest IC socket available usually has 8 pins; so don't worry if you damage a pin while removing it from the hard plastic socket. The pins of the wire-wrap socket are about 1 long, thereby making soldering them easier than standard sockets. Next, solder a 'fork' from thin rigid metal wires, to hold the four IC pins spaced at exactly 2 mm while you glue them together with superglue. Glue a plastic 'handle' to the four IC pins to be able to remove the connector from the HP48. You can also indicate the top side of the connector on this handle. Note that the hole in the HP48 in which the connector should go is not symmetrical; the pins are nearer to the top of the calculator than the bottom, and you can use this to make it difficult to insert the connector the wrong way up. Connector to plug in your HP48 (F) HP48 connector (M) ______ ______ |oooo| |....| ____/ ____/ pin 4 pin 1 pin 1 pin 4 MAKING THE CONNECTIONS You can use either a 9 or a 25 pin female sub-D socket for the PC-side of the cable. 9-pin RS232 25-pin RS232 connector (F) connector (F) pin 5 pin 1 pin 13 pin 1 ------------- --------------------------- | o o o o o | | o o o o o o o o o o o o | o o o o / o o o o o o o o o o o / --------- ----------------------- pin 9 pin 6 pin 25 pin 14 Use flexible 4-wire cable to connect the four contacts of your HP48 connector to the PC connector. Pin 1 of the HP48 should be connected to the metal shield of the RS232 connector. Usually it is not easy to solder this shield; first scratching the shield bare (it has some kind of coating) using a screwdriver or a file will help. If this doesn't work, simply leave pin 1 of the HP48 disconnected. Note that pins 2 and 3 of the RS232 connector must be swapped when you use a 25-pin connector. HP to PC cable HP48 | RS232-9 | RS232-25 -----+---------+---------- 1 | shield | shield 2 | 2 | 3 3 | 3 | 2 4 | 5 | 7 Before connecting the completed cable to your HP48, check for short-circuits using an ohmmeter or multimeter set to ohms or diode test. HP TO HP CABLE If you want to use 9600 bps communication between two HP48s, then make two HP48 connectors and simply connect the two, swapping pins two and three. HP to HP cable HP#1 | HP#2 -----+----- 1 | 1 2 | 3 3 | 2 4 | 4 WARRANTY, DISCLAIMER ETC. Although the serial interface of the HP48 is protected internally, it is possible to damage the calculator when a wrong connection is made. I am not responsible for any errors in this file, or for any mistakes you may make. ****************************************************************** END PART 3 OF 4