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comp.sys.hp48 FAQ : 3 of 4 - Appendices

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Andre Schoorl

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May 16, 1999, 3:00:00 AM5/16/99

Archive-name: hp/hp48-faq/part3
Last-modified: 5/16/1999
Version: 4.59
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post72
9.1. ASC Functions

Note: Although this document mentions SX only, ASC\-> and \->ASC work
on both the SX and GX.

From: Bill Wickes

ASCII Encoding HP48 SX Objects

Sending an HP48 SX 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 HP48 SX
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 e-mail 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 HP48 translate mode 3 so that the HP48 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 HP48
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 (if you have problems
with this and you are using the HTML version of the FAQ, you may wish
to try the plain text version or download a binary copy of the
program):

%%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

Installation instructions:

1. Save the above text 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 HP48 SX 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 HP48 SX in binary transfer mode before
uploading.

Disclaimers:

o 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\->.

o 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...

o 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.

9.2. OBJFIX

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 and 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 artificially contrived cases. Try both on real-world downloads
that need fixing. Which do you like better?

OBJFIX.ASC

%%HP: T(3)A(D)F(.);
"D9D202BA81D9F81B2040D9D20F2A26DA91629C8145126489162C23072C80CCD2
0BD0008FB9760147108134164142C2818F24D534501008B2F41643150D73B840
58405438314A161966D2BF6BF6A6F5BE16314213114334CF8208A6F58F235A04
55136D7D4EA494D231A1CA101110131CA130DBE284F8FC0760D41198F29960D4
130142119EA1408F5E0108D341503223072D70B2130B21301460"

9.3. FIXIT

From: Joe Horn and Mika Heiskanen

PURPOSE:
Converts a badly uploaded string into the original object.

THEORY:
A lot of folks upload HP48 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 HP48 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 HP48 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:

o No error: the object was extracted successfully and is on level
1.

o "Bad Argument Type" error: you didn't have a string on level 1.

o "Bad Argument Value" error: the string wasn't of the proper
form; it must be an "HPHP48-..." downloaded string.

o "Invalid Definition" error: the object was mangled in
transmission so badly that its end was lost; the object cannot
be extracted.

o "Undefined Result" error: there is no HP48 object in the string.

o "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 HP48 and get into it.

o 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 >>

o Press WTAV; see another garbage download. But EDIT refuses; the
string contains null characters. Press FIXIT; see successfully
extracted directory.

o 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.

o 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.

FIXIT.ASC

%%HP: T(3)A(D)F(.);
"69A20FF7CE20000000402414442340C2A203B000840584054383D25403A20FF7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"

9.4. LASTX

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. Note however that LASTX
uses the built in last argument feature, so if you use LASTX you will
lose the contents of your LASTARG.

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 HP48
@
%%HP: T(3)A(D)F(.);
\<< DEPTH \-> n
\<< LASTARG DEPTH n
- DUP \-> s
\<< ROLLD s 1 -
DROPN
\>>
\>>
\>>

9.5. Compact Data Storage

From: Jim Donnelly

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 HP48 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:

o Fields may be 0-length using this technique.

o The execution time is uniform across all fields.

o This technique saves about 4 bytes per field after the first field,
because the string prologue 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 char. data 5, NOT the
string "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 + 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
>>
>>

Alternative Solution to the Problem:
From: Matjaz Vencelj <ven...@fmf.uni-lj.si>

Jim allocates two bytes for each index entry (to handle longer
strings), but on the other side obviously only uses values
00...FF for index dublets, which just doesn't make sense. He's
at a 16*16 = 255 chars limit again!

I have put together a working set of commands which support up
to 65K strings, using two-byte indexing.

The encoder (Encode) is User-RPL program which calls the binary
N2C which converts the level 1 real into a 2 character string:

@*** Encode ***
%%HP: T(3)A(R)F(.);
\<<
IF DUP TYPE 0 = THEN 514 DOERR END
\-> N
\<<
N 1 + 2 * #18CEAh SYSEVAL #45676h SYSEVAL
1 N FOR I I 2 * 1 - OVER SIZE 1 + N2C REPL SWAP + NEXT
N 2 * 1 + OVER SIZE 1 + N2C REPL
\>>
\>>

@*** N2C, cksum=#8919h ***
%%HP: T(3)A(R)F(.);
"D9D202BA812BF819FF30D9D20AEC8111920001007FE3057A50C57463223057A5
0EE250B2130B21307206"

ASCII download them with translate code 3, then call program
'Encode' with data strings in levels 2..n+1 and a real n in level 1
indicating the number of strings.

The string decoder (Decode), which is usually speed-critical, is
the following \->ASC encoded binary:

@*** Decode, cksum=#38E1h ***
%%HP: T(3)A(R)F(.);
"D9D20D8A81D9F811192013000D9D20AEC8113D26CA130F6E30CA130E0E305080
311920001002CE30CAF0650803CBD30CAF06FED30F6E30CA130E0E3050803119
20001002CE30CAF0650803CBD30E0E3033750B2130B21309534"

It takes a `database' string on level 2 and a real (record
position) on level 1, then comes back with the appropriate
substring (record).

9.6. HP82240B Printer Codes

From: Jarno Peschier

Size of physical row
One printed row is either 24 normal characters, 12 expanded
characters or 168 pixels wide. This means that one normal
character has a width of 7 pixels. Any printed data "falling off
the row" will be truncated and ignored by the printer.

Reset

ESC 255d

This resets the printer to the following state: Roman8 character
set (watch out: the power-up character set is ECMA94), both
expanded and underline printing off, buffer cleared.

Self test

ESC 254d

This causes the printer to print a selftest pattern. This mainly
consists of a printout of the Roman8 character set.

Expanded printing

ESC 253d

This turns expanded printing on. This means that from this code on
all characters that are printed will be printed at twice the normal
character width because each column of pixels is printed twice.
Has no effect if expanded printing is already on.

ESC 252d

This turns expanded printing off. This means that from this code
on all characters that are printed at normal character width again.
Has no effect if expanded printing is already off.

Underlined printing

ESC 251d

This turns underlined printing on. This means that from this code
on all characters that are printed will be underlined because the
bottom-most pixel in each columns of pixels is now always on. Has
no effect if underlined printing is already on.

ESC 250d

This turns underlined printing off. This means that from this code
on all characters that are printed will not be underlined anymore.
The bottom-most pixel in each columns of pixels is printed as it is
defined for the printed character. Has no effect if underlined
printing is already off.

Character sets

ESC 249d

This switches the printer to use the ECMA94 character set. This
set is 100% identical to the character set used in HP48 calcula-
tors. This is the power up default of the printer. Has no effect
if ECMA94 is the current character set already.

ESC 248d

This switches the printer to use the Roman8 character set. This
set is different than the character set used in HP48 calculators in
the 128 last characters. As far as I know this set is used by
older printers like the HP82240A and by HP28 calculators (hence the
need for the OLDPRT command in HP48 calculators if you are printing
to a HP82240A). This character set is turned on if you reset the
printer with the reset code. Has no effect if Roman8 is the cur-
rent character set already.

Graphics

ESC n data (with n between 1 and 247)

This causes the printer to print graphics specified by the speci-
fied data (one byte per pixel column). The value n specifies the
number of bytes of data that follow the printer code that will be
interpreted as graphics data. Any data after pixel column 168 will
be truncated and ignored.

10. Appendix B: GX Specific Information

10.1. What's new in the HP48 G/GX?

From: Joe Horn

AUTOMATIC LIST PROCESSING
Almost all commands that did not accept list(s) as 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 --> { 1 4 9 }
{ 2 4 } 10 / --> { .2 .4 }
10 { 2 4 } / --> { 5 2.5 }
{ 10 12 } { 2 4 } / --> { 5 3 }
{ .1 .2 .5 } ->Q --> { '1/10' '1/5' '1/2' }
{ freq freq ...} { dur dur ... } BEEP can play a song with no
audible hiccup between tones.

Since + has always been used to concatenate lists, a new ADD func-
tion 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.

The only commands which do not have automatic list processing are:

o those which never get a Bad Argument Type error (like DUP),

o meta-object commands (like ROLL),

o program branch structures (like FOR), and

o commands that specifically work on lists (like GET).

Sometimes the results are non-obvious, for example:

5 { A B C } STO --> A=5, B=5, C=5
{ 5 6 7 } 'A' STO --> A={ 5 6 7 } (same as on SX)
{ 5 6 7 } { A B C } STO --> A=5, B=6, C=7

List processing is only recursive for ->Q and ->Qpi.

PORTS AND MEMORY
The HP48 G, like the 48 S, only has 32K RAM. The GX, unlike the
SX, has 128K RAM built-in. Card slot 1 can contain another 128K
(maximum), but card slot 2 can contain up to 4 megabytes of RAM.

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 HP48 SX
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.

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.

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.

IMPROVED COMMANDS:

o AXES can now also specify the spacing of the tick marks.

o DEPND can now also specify the initial values and tolerance for
the new DIFFEQ plot type.

o REPL and SUB now work on arrays.

HP SOLVE EQUATION LIBRARY CARD COMMANDS:

o AMORT, amortization calculations

o CONLIB, starts Constants Library catalog

o CONST, returns value of a named CONLIB constant

o DARCY, calculates Darcy friction factor

o EQNLIB, starts Equation Library catalog

o F0lambda, calculates black-body power fraction

o FANNING, calculates Fanning friction factor

o LIBEVAL is a generalized form of the EQ card's ELSYSEVAL; it
executes any XLIB by its library number

o MCALC, marks an MSOLVR variable as "not user-defined"

o MINEHUNT, starts the "Minehunt" video game

o MINIT, initializes Mpar from 'EQ' for MSOLVR

o MITM, customizes title & menu of MSOLVR's screen

o MROOT, solve for variable(s) in MSOLVR

o MSOLVR, shows Multiple Equation Solver menu

o MUSER, marks an MSOLVR variable as "user-defined"

o SIDENS, density of silicon as function of temperature

o SOLVEQN, starts solver for specified EqLib equation(s)

o TDELTA, subtracts temperatures like "-" ought to but doesn't

o TINC, adds temperatures like "+" ought to but doesn't

o TVM, shows the financial calculator (Time Value of Money) menu

o TVMBEG, sets payments-at-beginning-of-periods mode

o TVMEND, sets payments-at-end-of-periods mode

o TVMROOT, solves for a TVM variable

o ZFACTOR, calculates gas compressibility factor Z

Note: The EQ Card's Periodic Table and Tetris game are not in
the HP48 G/GX, but the EQ Card can be used in the GX if those
applications are needed. Tetris was not included because no
agreement on royalty was reached. The Periodic Table is
available separately as freeware on HPCVBBS.

NEW ARRAY COMMANDS:

o COL+, inserts a column vector into a matrix or a number into a
vector (like INSCOL/PUTCOL in Donnelly's Tool Library)

o COL-, deletes a column from a matrix or number from a vector
(identical to DELCOL in Donnelly's Tool Library)

o COL->, combines multiple column vectors into a matrix

o ->COL, breaks a matrix into multiple column vectors (like
repeated GETCOL in Donnelly's Tool Library)

o COND, column norm condition number of a square matrix

o CSWP, swaps two columns in a matrix (like EXCOL in Donnelly's
Tool Library)

o ->DIAG, returns vector of major diagonal elements of a matrix

o DIAG->, creates matrix with specified diagonal elements

o EGV, eigenvalues and right eigenvectors of a square matrix

o EGVL, eigenvalues of a square matrix

o FFT, discrete Fourier transform

o IFFT, inverse discrete Fourier transform

o LQ, returns the LQ factorization of a matrix

o LSQ, minimum norm least-squares solution to an ill-determined
system of linear equations

o LU, returns the Crout LU decomposition of a square matrix

o PCOEF, returns polynomial with given roots (inverse of PROOT)

o PEVAL, evaluates polynomial at x

o PROOT, finds all roots of polynomial (inverse of PCOEF)

o QR, returns QR factorization of a matrix

o RANK, rank of a rectangular matrix (uses flag -54)

o RANM, creates matrix with random elements

o RCI, multiplies elements in one row of a matrix by a scalar

o RCIJ, does RCI then adds the result to a row

o ROW+, inserts a row vector into a matrix or a number into a
vector (like INSROW/PUTROW in Donnelly's Tool Library)

o ROW-, deletes a row from a matrix or number from a vector
(identical to DELROW in Donnelly's Tool Library)

o ROW->, combines multiple row vectors into a matrix

o ->ROW, breaks a matrix into multiple row vectors (like repeated
GETROW in Donnelly's Tool Library)

o RSWP, swaps two rows in a matrix (identical to EXROW in
Donnelly's Tool Library)

o SCHUR, computes the Schur decomposition of a square matrix

o SNRM, spectral norm of an array

o SRAD, spectral radius of a square matrix

o SVD, singular value decomposition of a matrix

o SVL, computes the singular values of a matrix

o TRACE, sum of diagonal elements of a square matrix

GRAPHICS and PLOTTING COMMANDS:

o 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!

o ATICK, specifies tick spacing on plot axes

o EYEPT, specifies the eye-point coordinates in a perspective plot

o GRIDMAP, selects the new "gridmap" plot type

o PARSURFACE, selects the new "parametric surface" plot type

o PCONTOUR, selects the new "pcontour" plot type

o PICTURE, same as GRAPH command

o SLOPEFIELD, selects the new "slopefield" plot type

o WIREFRAME, selects the new "wireframe" plot type

o XVOL, sets the width of the 3D plotting volume

o XXRNG, sets the width of the 3D target mapping range for gridmap
and parametric surface plots

o YSLICE, selects the new "yslice" plot type

o YVOL, sets the depth of the 3D plotting volume

o YYRNG, sets the depth of the 3D target mapping range for gridmap
and parametric surface plots

o ZVOL, sets the height of the 3D plotting volume

USER-INTERFACE COMMANDS:

o CHOOSE, displays a point-and-click menu "dialog box"

o INFORM, formatted multi-line input with named fields (nice!!)

o MSGBOX, displays text in a centred box with shadow, then WAITs

o NOVAL, placeholder for unspecified values in INFORM argument
list

LIST PROCESSING COMMANDS:

o ADD, adds lists element-wise (see section above)

o DOLIST, evals an object on multiple lists

o DOSUBS, evals a program or command taking arguments from a list

o ENDSUBS, returns the number of loops the current DOSUBS will do

o HEAD, first element in a list or first char in a string
(identical to CAR in Donnelly's Tool Library)

o DeltaLIST, list of first finite differences of list objects

o SigmaLIST, sum of the elements in a list

o PiLIST, product of the elements in a list

o NSUB, returns the current list pointer value during a DOSUBS

o REVLIST, reverses the order of the objects in a list (like
REVERSE in Donnelly's Tool Library)

o SEQ, list of results from repeated execution of an object (like
a FOR/STEP loop but the results go into a list)

o 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)

o 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.

o TAIL, returns a decapitated list or string (see HEAD above)
(identical to CDR in Donnelly's Tool Library)

SYSTEM COMMANDS:

o CLTEACH, clears the 'EXAMPLES' directory created by TEACH

o CYLIN, sets polar/cylindrical coordinate mode

o FREE1, like 1 FREE (see section above)

o MERGE1, like 1 MERGE (see section above)

o PINIT, port initialize, esp. important for 4-Meg RAM card users

o RECT, sets rectangular coordinate mode

o SPHERE, sets polar/spherical coordinate mode

o TEACH, loads the Owner's Manual examples into a dir in HOME

o VERSION, returns the operating system ROM version string and a
copyright notice, like this:

2: "Version HP48-R" <-- means version "R"
1: "Copyright HP 1993"

o XRECV, X-Modem protocol receive (binary mode only)

o XSEND, X-Modem protocol send (binary mode only)

MATH COMMANDS:

o LININ, tests whether an equation is linear in a given variable

o NDIST, normal probability density

o PCOV, population covariance of SigmaDAT

o PSDEV, population standard deviation of SigmaDAT

o PVAR, population variance of SigmaDAT

o RKF, solves initial value problem using Runge-Kutta-Fehlberg

o RKFERR, change in solution and absolute error using RKF

o RKFSTEP, next solution step with given error tolerance using RKF

o RRK, solves initial value problem using Rosenbrock & RKF

o RRKSTEP, next solution step with given error tolerance using RRK

o RSBERR, change in solution and absolute error using Rosenbrock

MENU NUMBERS and KEY CODES
Many menu numbers have changed, so software that uses # MENU or
# TMENU may not work the same as in the HP48 S/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 colour change to match the
very dark green of the calculator case.

MANUALS
The G/GX comes with two manuals, a "Quick Start Guide" for
beginners, and a cost-cutting, slimmer owner's manual called the
"User's Guide" which has only 21 pages about programming, since
HP figures that the huge majority of all 48 owners never program
it anyway. The power users can buy the optional "Advanced Users
Reference Manual" (similar to the S/SX's "Programmer's Reference
Manual") which covers programming and the many commands that are
not mentioned in the User's Guide. There is no "Quick Reference
Guide" like the S/SX came with, although the case still has a
pocket for one.

Jim Donnelly has marketed a nice pocket guide, but it's too wide
to fit in the case's pocket. The User's Guide is not spiral
bound, but is made to open fully and last a long time, since
it's not just glued but has sewn signatures like real books, and
is printed on quality paper.

Another possibility is "The HP 48G/GX Pocket Guide" by Chris
Coffin and Thomas Dick (Grapevine Publications). It's 80 pages
long, contains a complete command reference (with input/output
stack diagrams), alpha keyboard description, system flag
description, as well as examples of how to use various
calculator features. This guide is designed to fit nicely in
the pocket of the HP case.

FLAGS
Some previously "unused" flags are now used. They are:

-14 Clear = end-of-period payment mode (for TVM calculations)
Set = beginning-of-period payment mode

-27 Clear = display symbolic complex numbers in coordinate form
e.g. '(X,Y)'
Set = display symbolic complex numbers using 'i'
e.g. 'X+Y*i'

-28 Clear = plot multiple equations like the S/SX does (serially)
Set = plot multiple equations simultaneously

-29 Clear = include axes in plots (like the S/SX does)
Set = omit axes from 2D and statistics plots

-30 is no longer used (it never did anything useful anyhow)

-54 Clear = tiny matrix elements get rounded to zero
Set = leaves matrix elements alone

The default setting of all these flags is Clear (as in the S/SX).

FLAG BROWSER
There is a System Flag browser which shows the flag number,
shows whether it's set or clear, lets you toggle it, and shows
in English what the current setting means.

CHARACTER BROWSER
While programming, if you want to type any character at all,
press CHARS and a screenful of ASCII characters is displayed
that you can browse with the arrow keys, and not only does the
screen also show the ASCII code (NUM value) and even the
shortcut keyboard key sequence (if any) for each character, but
if you press ECHO, it will be "typed" into your program.
There's no need any more for the alpha keyboard table.

DIRECTORY MAINTENANCE
Press right-shift VAR to launch a Variable Browser which is a
complete memory manager. You can tag multiple objects and copy,
move, or delete them all with a single keystroke; there's even a
Mark All and an Unmark All, like a real computer. It's slow,
however, and has been obsoleted by the very fast PCT library.

FRACTIONAL UNIT POWERS
The S/SX only handled integer powers of units correctly, but the
G/GX can use any real number as a unit power.

NAME PLATE
The case has a rectangular indentation in the back like the HP
95LX and 100LX, and it comes with an adhesive metal nameplate
that you can get engraved with your name.

XLIB NAMES
All of the new commands in the GX are XLIB names, and therefore
take 5.5 bytes in programs. The commands common to the SX and
GX take 2.5 bytes each, as they did in the SX.

INPUT FORMS and CHOOSE BOXES
Many operations have two menu types: the old SX style, and a new
"drop-down" menu and "input forms" that have the feel of
computer dialog boxes. Especially useful for the HP48 beginner.

ENHANCED PRECISION
The internal precision of at least some of the matrix routines
has been improved; INV gets better answers on square matrices
than the SX did. HP has not released information about which
routines were improved, how, and by how much.

IMPROVED DISPLAY
The LCD introduced with revision M of the G/GX is easier to read
since it has higher contrast between on/off pixels. It has a
slower cycle response time, however, making it difficult to use
for rapid-motion video games or any other rapid animation.

10.2. Examples of INFORM, CHOOSE, and MSGBOX

From: Jarno Peschier

Some examples of INFORM, CHOOSE and MSGBOX on the HP48 GX. Just
download the entire directory to your calculator and try the programs,
change them, modify them and do everything else with them you can
think of.

SIMPLE:
This program will demonstrate a simple INFORM input screen with
3 fields (one without type restrictions, one for real or complex
numbers and one for strings) with some additional layout. MSGBOX
and CHOOSE (with the third parameter equal 0) are used to show
what the results of the INFORM command are. The list the INFORM
command returns is left on stack so you can see what it looks
like.

ANGLE:
This program will demonstrate the use of CHOOSE. It lets you
choose between the three possible angle modes (DEG, RAD, GRAD)
and when you choose one of them, the corresponding mode is set
by evaluating a tiny program containing the right command.

ISOLATE:
This program will demonstrate the use of INFORM in ways that it
is used in the calculator itself. It is a very simple shell
around the ISOL command (isolation of a variable from an
algebraic). It remembers it's settings in a variable called IPAR
and the next time the program is run this will be the default
values of the INFORM command, so you can isolate for a different
variable using the same algebraic you used before, without
retyping it. MSGBOX is used for error messages.

TYPELIST:
This program will again demonstrate the use of CHOOSE. It
extracts the names of all the internal types of the HP48 GX from
ROM and shows them in a CHOOSE-box (alphabetically sorted by
name). If you choose one of them, its TYPE number is shown in a
MSGBOX.

MATHQUIZ:
This final program will demonstrate the use of INFORM with
variable field descriptions and default/reset values. It's will
show you 8 fields that are simple math questions for you to
solve (addition and subtraction). You can enter all the results
and then you will see if your answers were correct (in a
MSGBOX). You must fill all the fields. Hint: you can cheat by
resetting a field (or all fields).

%%HP: T(3)A(D)F(.);
DIR
SIMPLE
\<<
IF
"AN EXAMPLE OF INFORM"
{ { } { } { } {
"OBJECT:"
"ALL OBJECTS ARE ALLOWED HERE"
} { } { "NUM:"
"ENTER A (COMPLEX) NUMBER"
0 1 } { "NAME:"
"ENTER YOUR FULL NAME"
2 } { } { } } { 3 1
} {
\<< 440 1
BEEP
\>> (0,1)
"JARNO PESCHIER" }
{ NOVAL 0 "N.N." }
INFORM
THEN DUP
"YOU ENTERED:" SWAP
0 CHOOSE DROP
"The list that INFORM produced is still on the stack."
ELSE
"You cancelled the INFORM."
END MSGBOX
\>>
ANGLE
\<<
IF
"ANGLE MEASURE" { {
"Degrees" DEG } {
"Radians" RAD } {
"Grads" GRAD } } 1
CHOOSE
THEN EVAL
END
\>>
ISOLATE
\<<
IF
"A VERY SIMPLE VARIABLE ISOLATOR"
{ { } { "EXPR:"
"ENTER THE EXPRESSION"
9 } { "VARIABLE:"
"ENTER VARIABLE TO ISOLATE"
6 } } { } { }
IF 'IPAR'
VTYPE 5 \=/
THEN { }
ELSE 'IPAR'
RCL
END INFORM
THEN DUP 'IPAR' STO
IF DUP
NOVAL POS
THEN DROP
"You must enter an expression and a variable!"
MSGBOX
ELSE OBJ\->
DROP
IFERR
ISOL
THEN
DROP2 "Error: "
ERRM + MSGBOX
END
END
END
\>>
TYPELIST
\<<
IF
"ALL HP48 TYPES (IN ROM)"
0 27
FOR msg
IFERR msg
263 + DOERR
THEN ERRM
END msg 2
\->LIST
NEXT 28
\->LIST SORT 1 CHOOSE
THEN
"That one has type number "
SWAP + "." + MSGBOX
END
\>>
MATHQUIZ
\<<
IF
"A SIMPLE MATH QUIZ"
1 8
FOR i "'"
RAND 100 * IP +
IF RAND
0.75 <
THEN "+"
ELSE "-"
END +
RAND 100 * IP + "'"
+ "ENTER RESULT #"
i + 0 3 \->LIST
NEXT 8
\->LIST DUP
\<< \-> X
\<< X HEAD
2 OVER SIZE 1 - SUB
"=" + X 1 ROT PUT
\>>
\>> DOLIST
SWAP
\<< \-> X
\<< X HEAD
OBJ\-> EVAL
\>>
\>> DOLIST 3
ROLLD { 2 5 } 4
PICK { } INFORM
THEN
IF DUP
NOVAL POS
THEN DROP2
"You didn't fill all the blanks."
ELSE
IF SAME
THEN
"All answers were correct!"
ELSE
"Not all answers were correct."
END
END MSGBOX
ELSE DROP
END
\>>
END

10.3. Some useful LIBEVALs

From: Joe Horn

Note well: backup memory before using any of the following! LIBEVAL
can clear memory if used incorrectly. Warning to the clueless:
LIBEVAL, NOT SYSEVAL!!! If you don't know what a "bint" is, don't use
the ones that mention bints.

Example usage: "OUT OF RANGE Try Again" #B0091h LIBEVAL. Try it!

LIBEVAL : stack diagram / what it does
------- -----------------------------------------------------------
#B0091h : $ --> makes a message box with an alert symbol in it
#E0044h : $ --> displays a title line, top center (follow with
1 FREEZE if you want it to stay there after program ends)
#B2000h : launches the Last Command choose-box
#B2001h : launches the CHARS application; returns nothing if user does
not press ECHO
#B2002h : launches the CHARS application; returns "" if user does not
press ECHO
#B41CFh : launches Flag Browser; leaves a True or False on stack, so
follow this LIBEVAL with a DROP.
#B50A3h : --> current time as hour, min, sec separately, plus an XLIB
that represents AM/PM/24-hr (just DROP it)
#B50A4h : hh.mmss --> hh mm ss xlib (the xlib represents AM,PM, or
24-hr mode; just DROP it)
#B50A6h : --> current date as month, day, year (always that order, and
a two-digit year)
#B50A7h : mm.ddyyyy (or dd.mmyyyy) --> month, day, yr
#B50A9h : #month #yr --> #days_in_that_month (inputs and output are
bints; year is two digits, interpreted as between 1991 &
2090 only)
#B50AAh : #yr --> %0.00yyyy (input is two-digit bint interpreted as
between 1991 and 2090; output is a real number)
#B50ABh : #mon #day #yr --> #day_of_week (inputs & output are bints;
year is two digits interpreted as between 1991 & 2090;
Sunday is #7; if you're in DMY mode, then the input order is
#day #mon #yr)
#B50B2h : --> { 1 2 3 ... 59 } (not very fast)
#B50B3h : --> { 1 2 3 ... 10 } (very fast)
#B50B4h : --> { 0 1 2 ... 23 } (very fast)
#B50B9h : --> { " 1 January" " 2 February" ... "12 December" }
#B50D5h : --> number of alarms currently set (as a bint)
#E3063h : hxs --> grob (this is an RLL packed-grob uncompressor, used
by EQ LIB and MINEHUNT; for example, try this:
#E202Bh LIBEVAL 3 GET #E3063h LIBEVAL PICT STO PICTURE)
#E202Bh : the first of the packed EQ LIB grobs (see above)
#E2069h : the last of the packed EQ LIB grobs (see above)
#E7039h : MINEHUNT packed grob (left screen border)
#E703Ah : MINEHUNT packed grob (right screen border)
#E801Eh : obj --> obj T/F (tests whether object is in temporary memory
or not; returns System-RPL True or False)

11. Appendix C: Details of Bugs

11.1. The EquationWriter Bug

From: Joe Horn

Rev E Behaviour
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 Behaviour
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 Paren-
theses" 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.

11.2. Rotation Rate to Angular Frequency Conversion Bug

About the Bug:
From: Wlodek Mier-Jedrzejowicz <wa...@doc.ic.ac.uk>

There is a rotation rate conversion bug in the HP48 G/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 HP48 G/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 HP48 S/SX that is the
answer. On an HP48 G/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 HP48 S/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 HP48 G/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 preceeded 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 HP48 S/SX.

So, when you convert 60_rpm to units of _r/s, an HP48 G/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 HP48 GX. 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 HP48 SX was not much better,
since it converted from radians to unit circles. The way to get
the correct answer is to use an HP48 G 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 HP48 G/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 HP48
G/GX or get on a high horse and demand that HP replace your HP48
G/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 HP48 S/SX; to see this on an HP48 S/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 HP48 G/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
HP48 G/GX!

The whole subject gets very little mention in HP's manuals. In
the original HP48 SX 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 HP48 S and HP48 SX manual (one volume), the same warning
is given in "Converting Dimensionless Units of Angle", on page
13-12. The HP48 G 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 HP48 S/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 HP48 SX,
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 HP48 S/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 HP48 G/GX team read this while they were
making changes from the HP48 S/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 HP48 S/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 HP48 G/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 HP48 G/GX version of the
book!

I have not yet mentioned solid angles. In principle there should
be no problem - on both the HP48 S/SX and the HP48 G/GX the base
unit of solid angle is a "unit sphere", or 4pi steradians. On
the HP48 S/SX you can add the pure number 1 to 0_sr and get
12.5664_sr (4pi steradians). The HP48 G/GX manuals imply that
exactly the same should happen, but on my (version L) HP48 GX
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.

Addition Insight:
From: Eric Haas <EH...@ix.netcom.com>

Note: The < symbol below is actually the angle character.

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_</s,
all conversions to and from rpms will work just fine. As an easy
work-around, define the unit RPM as 6_</s and use that instead
of the built-in unit.

If desired, one could also define the unit HZ as 60_rpm or
360_</s. However, as Hz is sometimes used to describe things
other than rotation rates, such a definition would not be
appropriate for all circumstances.

12. Appendix D: Hardware Additions

12.1. How to Make a Serial Cable

From: Frank Vorstenbosch <pro...@xs4all.nl> Revised by: Andrew Chen

Now that you have your HP, you probably want to tap the tremendous
amount of programs out there. But how do you do this? You need an HP
to PC link. You can buy one, but they tend to be fairly costly. Or
you can build your own. The process requires the following parts:

Required Parts:

o Soldering iron and flux

o RS232-9 or RS232-25 shield (serial port shield)

o RS232-9 or RS232-25 female connector (serial port connector)

o 4 pin HP connector, with sockets spaced 2 mm (NOT 0.1") apart

o Some copper wire

Of the above list of parts, most are pretty easy to acquire, and you
should be able to find them at your local electronics store. However,
the 4 pin (i.e. male) HP connector can be a bit harder to find.

If you happen to have a broken floppy drive, hard drive, or CD-ROM
audio cable 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 on your calculator.

HP Connector
The HP connector part of the cable will be the most frustrating
part of the link. The reason is that you will probably not be
able to find these at your local electronics store, but you
should you should find everything else there. Instead, you can
either find the connector at used computer stores or you can
create the link yourself.

Easy Way
Because the former is much easier, I will give you some tips
on where one can find the connecter. First, check your
yellow pages and look under "computer". You will find a lot
of stores, but look specifically for "computer repair" or
"computer parts". Call these stores asking for a "CD-ROM
audio cable". If the store carries these cables, go to the
store and ask to see the requested cable.

What you should see is a cable with two ends, each with a 4
socket connector. One end should be spaced a bit larger than
the other, and this one will not fit into the HP's pins
(don't press too hard, or else you will bend the connector
pins). The other side should fit like a charm. Don't be
worried about that there are only 3 sockets. This is fine
because the empty one is a ground. Once you have this cable,
cut off the unusable end, and go to the PC connector section.

Hard Way
If are unable to find a place that carries CD-ROM audio
cables, or you prefer to make your make, it is possible to
build the connector yourself. What you can do is buy IC
sockets from a local electronics store. You can usually find
them in packs of 8 or more. These IC sockets will be bound
together in a hard plastic shell, which also places at
unusable intervals. Therefore, it is necessary to strip the
IC sockets out of the hard plastic shell (don't worry too
much about damaging them, the IC sockets are fairly durable
and you have 8 of them).

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.

With that done, you can proceed on to the PC side of the
connector.

PC Connector
The PC side of the connector is much simpler than the HP side.
All you have to do is make a standard serial connector with the
parts you bought. However, don't do it yet because you need to
solder the wires from the HP connector into the back of the
serial connector first.

Making the Connections
Now that you have the two sections done, you can begin making
the connections for the actual link. Starting with the HP side,
put in the connector and mark the top as "UP". If you have a
CD-ROM audio cable with one socket missing, make sure that the
empty socket connects to pin 1:

Connector on HP48 Connector to HP48
______ ______
|....| |oooo| <-- First is
\____/ \____/ null
pin 1 pin 4 pin 4 pin 1

If you made the HP connector the hard way, you have to solder the
ends of the IC sockets to long pieces of wire, which will
eventually connect to the serial connector on the PC side of the
cable.

With these wires done, you must solder the individual wires into
the proper places on the PC side. Use this table of pin
connections:

HP to PC cable

HP48 | RS232-9 | RS232-25
-----+---------+----------
1 | shield | shield
2 | 2 | 3
3 | 3 | 2
4 | 5 | 7

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.

Before connecting the completed cable to your HP48, check for
short-circuits using an ohmmeter or multimeter set to ohms or
"diode test". The HP48 has a built in serial loop back test that
can be used to test the serial cable (see the question regarding
the ON-KEY combinations).

After you are done, close the shield and connector, and put in all
the screws. You should now have a HP<-->PC link, which functions
on COM (serial) ports.

Using the Link
With the link finished, it is now ready to be tested. Download
some programs (such as those in the Best Program List) that you
wish to try. At some point you should go to
<http://www.columbia.edu/kermit/> to obtain the version of
Kermit that suits you best.

However, if you have an alternate communications program (for
example, Windows 95 comes with HyperTerminal which you can use)
you can delay downloading Kermit. However, it is a highly
recommended to obtain because certain programs for the HP48 use
special features in Kermit (such as server mode) not available
in other communications programs.

With this done, you can begin the actual transfers. Start your
communications program, and set the port to COM1 (or whatever
your link is plugged into). In Kermit, you would type "SET PORT
COM1" and in HyperTerminal you would set the dialog box with the
choice of what modem you want to use to "Direct to COM1".

Then change the speeds of the ports to 9600. In Kermit, type
"SET SPEED 9600" and in Hyperterminal click on Advanced.

On the HP, go to I/O, and go to Transfer. Set the calculator to
Wire, 9600 baud, and Kermit (or X-Modem, if you using it
instead). Then, get ready for to receive a file. Note that X-
Modem is much faster than Kermit in most situations, especially
in long transfers. However, it is not available built-in on the
S/SX.

On the PC start sending, and on the HP, start receiving. You
should see the transfer arrow on the upper right of the screen
on the HP, and it should be flashing. On the PC, you should see
a progress indicator to show how much of the file has been
transferred.

When the transfer is finished, check that you received what you
expected. If it what you expected, your HP<-->PC link works!

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.

From: Deborah Lynn Williams

I made an HP48 link out of four pieces of speaker wire and serial port
plug. The wiring of the plug is available above. The connection to
the HP plug is the difficult part.

I took 4 pieces of stranded speaker wire and cut them so that the wire
and the insulation were even. I then took a paper clip and pushed it
into the this open end, making a space between the wire and the
insulation. I then had to trim some of the strands that were sticking
out. I then just pushed this onto the pins in the HP48 port. It
isn't a very strong connection, but it works fine if you don't jostle
it.

The other ends of these speaker wires I connected to the serial plug.
Just remember to label which wires go to which pin, or make them all
different lengths.

From: John Cutter

Another cheap source for cables is the common serial mouse for PC-
compatibles. I had a cheap one on which the button gave out after 2
weeks of use, so I opened it up. It had a serial 9 pin cable that
disappeared into the mouse. Once open, there was a 4 pin 2 mm
connector plugged into the mouse's circuit board. All I had to do was
reverse two pins inside the connector, and it's been working fine
since. I also noticed that Logitech mice have 6 pin 2 mm connectors,
which could also be adapted. No soldering or crimping here!

12.2. Using a modem with the HP48

From: Diego Berge

My purpose here is to explain in some detail the steps you need to
follow to be able to transmit data via modem with the HP48. Another
related document is
<http://www.freeweb.org/freeweb/enrico/hp2modem.htm> by Enrico Carta.

In order to successfully connect your HP48 calculator to a modem, the
first thing you need is a 'Null Modem Cable'. A null modem cable is
like a regular serial cable, except that two of its lines are crossed.

You might wonder: So why is it different connecting to a PC than
connecting to a modem? Well, data communication devices can be
classified in two groups: Devices which GENERATE or RECEIVE
information, and devices which merely TRANSMIT information. The
former are called Data Terminal Equipment (DTE), PCs are an example of
DTE; the later is called Data Communication Equipment (DCE), and are
primarily modems. Now, when PCs were designed, it seems like they
didn't think somebody would ever want to hook two DTEs directly, as a
result, in a typical PC all we have (besides the parallel printer
port) is an RS-232 port, which is intended for connecting a DCE. So
when a machine wants to connect to a PC, its port must be that of a
DCE, even if it otherwise acts as a DTE. Within that class of hybrids
fall HP48s, Psions, some (or most?) serial printers, mice, and a long
etcetera.

Remember, the RS-232 communication scheme is:

DTE <--- DCE === DCE ---> DTE

If you want to link two DTE together, you must 'simulate' a DCE;
that's what a Null Modem Cable is for. It's called 'Null' because it
(the modem) does not actually exist, and 'Modem' because it acts like
if there was one. To build a Null Modem Cable for the 48, assuming
that you already have a regular cable, you'll need two MALE RS-232C
connectors, at least one of which must be a DB-9 (9-pin), and a short
piece of mouse cable or similar (some 3 inches should do) (If you
don't have a regular cable, I recommend that you get one). The wiring
must be as shown here:

CONNECTOR 'A' CONNECTOR 'B'
pin#: 3 2 7 (DB-25)
pin#: 2 3 5 pin#: 2 3 5 (DB-9)
name: TX RX GND name: TX RX GND
| | | | | |
| | | | | |
| | +---------------------------------|---|---+
| | | | ( <<< and
| +------------------>>>----------------+ | >>> show
| | direction of
+----------------------<<<--------------------+ data )

The pin number should be embossed near the pin itself in the
connector.

Once the physical part is done, which in most cases will be the most
critical, you're ready to try out your brand-new, state-of-the-art,
$2.25 null modem cable. Plug it between your regular HP48 cable and
your modem, turn the modem on (please don't forget this part :), and
on the 48 type in:

[RightShift]+[""] [alpha] [alpha] AT [ENTER]
13 [LeftShift]+[CHARS] [CHR] [+]

In stack level 1 you should have (# is a little black square):

1: "AT#"

Now type:

[LeftShift]+[I/O] [NXT] [SERIAL] [XMIT] [BUFLEN] [DROP] [SRECV]

you should get:

2: "AT###OK##"
1: 1

If this test goes wrong, try two or three more times. If it still
fails, check your cable(s), check that the 48 can transmit and receive
to/from the PC, do the same with your modem. And when everything else
has failed anyway, connect your modem to the PC, crank up a terminal
program (as Terminal / Hyperterminal, or Kermit's 'Connect' command),
and type:

AT&D0 [ENTER]

the modem should respond:

This tells the modem to ignore the DTR signal from the host, which the
48 can't supply. Try again with the calculator, if it works, go back
to the terminal and type:

AT&W0&Y0 [ENTER]

to save the current modem configuration as default. If it has not
worked so far, I can't help you.

Assuming you've got it to work, now all you have to do is learn a few
modem commands to dial and, possibily, hang up. In general, modem
commands start with the two-character sequence 'AT' (no quotes) and
end with a single <CR> character (dec 13), <LF> is optional.

To dial a number use:

ATDT12345<CR>

where 12345 should be replaced by the actual number. For example:

[RightShift]+[""] [alpha] [alpha] ATDT0800890011 [ENTER]
13 [LeftShift]+[CHARS] [CHR] [+] [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]

dials the AT&T Direct access number for the UK.

If your line is not connected to a digital switchboard, you may need
to dial by pulses, then you should use instead:

ATDP12345<CR>

Next thing you'll probably ask is: 'How do I know that I'm connected?'

If the modem has successfully established a connection, it should
respond in most cases with a message like:

CONNECT 9600/V34/LAPM/V42BIS/9600:TX/9600:RX

or simply "1" if its not in the default verbose mode. Also, if the
modem has a 'CD' indicator, it'll usually light up. To find out via
the calculator whether it's connected or a problem has occurred, use
the following keystrokes:

( [LeftShift]+[I/O] [NXT] [SERIAL] )
[BUFLEN] [DROP] [SRECV]

repeatedly until a non-empty string appears in level 2. Some common
messages are:

verbose: non-verbose:

CONNECT 1
NO CARRIER 3
ERROR 4
NO DIALTONE 6
BUSY 7
NO ANSWER 8
DELAYED 24

Once you get the CONNECT message, you're ready to send any data you
want to the remote host as you'd usually do. I personally use Kermit
this way when I'm not in the office or at home.

Finally, when you're done you'll want to hang up the line. The
simplest way is turn the modem off, which I recommend. But if you
want to instruct the modem to hang up, the process usually is:

(wait at least 1 sec without sending any data)

[RightShift]+[""] [alpha] [alpha] +++ [ENTER]
[LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]

(wait at least 1 sec without sending any data)

[RightShift]+[""] [alpha] [alpha] ATH [ENTER]
13 [LeftShift]+[CHARS] [CHR] [+] [LeftShift]+[I/O] [NXT] [SERIAL] [XMIT]

Note, however, that this, as most of what I have said here about modem
commands, might vary depending on each modem's particular brand, model
and configuration. You may need to read your modem's manual for more
details.

Disclaimer: As you'd expect, I take no responsibility for anything you
may break, twist, cut, slice, burn, hurt, or otherwise damage while
following these instructions.

12.3. Additional Information on the HP48 and RS-232

From: John Meyers

You can't connect the HP48 to anything else until you have first
plugged in its cable, which finally brings the HP48's serial
connections out to a DB9 connector. At that point, the HP48,
including its attached cable, is clearly configured as DCE (the same
as a modem), so you need a "crossover" (such as a "null-modem
adapter") to connect the HP48 to a modem.
12.4. Using Non-HP RAM Cards

If you use RAM cards that are NOT designed for the HP48, it is
possible to severely damage your HP48. If you want to be safe, you
should only use RAM cards designed for the HP48.

Here is an edited discussion from comp.sys.handhelds.

From ste...@hpcvra.cv.hp.com Fri Mar 1 17:00:00 1991
From: ste...@hpcvra.cv.hp.com (Steve Harper)
Date: Thu, 10 May 1990 22:46:09 GMT
Subject: RE: HP48 SX Memory Card Pricing
Organization: Hewlett-Packard Co., Corvallis, OR, USA

There has been a substantial amount of comment regarding the memory
cards for the HP48 SX 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 I/O 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 HP48
SX. Other memory cards exist which are mechanically compatible with
the HP48 S, but these cards cannot be relied upon to work electrically
in the calculator. The HP48 SX 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 ste...@hpcvra.cv.hp.com Fri Mar 1 17:00:00 1991
From: ste...@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-HP48 SX
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-HP48 SX 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 HP48 SX 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 HP48 SX 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 HP48 SX cards are
not at all out of line.

Steve "I claim all disclaimers..."

From pres...@hpcvra.cv.hp.com Fri Mar 1 17:00:00 1991
From: pres...@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 specified to be 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 through 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

12.5. Where can one obtain third party RAM cards?

If you decide you want to look into the non-mainstream alternatives
for RAM cards, you might like to check the following URLs:

o <http://www.cynox.de/>

o <http://stolte-edv.com/de/>

o <http://www.cyberline.de/kkgbr/>

o <http://www.Digitalis.de/>

o <http://home.t-online.de/home/FFFFF/>

o <http://www.geocities.com/Eureka/Enterprises/3190/>

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