frank@zen.UUCP (Frank Wales) (03/04/88)
[This is posted on behalf of a friend who has no access to Usenet; please direct any replies to one of the addresses at the end. frank] Here are some more notes on the HP-28C, HP-28S, and a book about them. 1. Careful use of SYSEVAL has led to discoveries of useful routines in the HP-28C and HP-28S ROMs, but SYSEVAL can also be used to locate the RAM, and the (separate) display RAM. Users who have gone from an HP-28C to an HP-28S may like to know that the display RAM has moved from the address range #40000 - #47FFF to #FF800 - #FFFFF on the 28S. 2. The user RAM was at #4F000 - #4FFFF on the 28C. On the 28S it is at #C0000 - #CFFFF. Although the amount of RAM has gone up from 2K to 32K, about 400 bytes are reserved for the system, so in fact the HP-28S provides 17 times more RAM available to the user! Oddly enough, the HP-28S user RAM can also be accessed at addresses #D0000 - #DFFFF. This suggests HP designed the HP-28S with two "memory controllers", each able to control 32K of RAM, but in the end they provided only one 32K block, and therefore had to hardwire BOTH controllers to it, otherwise there would have been a controller claiming to provide 32K RAM, but unable to come up with the goods. 64K RAM in a pocket calculator would have been amazing, but with no input method (except the keyboard) it would hardly have been worth it. It seems to me that with the HP-27S now available as an alternative to the HP-28C at a fairly low (for HP) price, they should have produced a more expensive version of the HP-28C with more memory AND some useful means of interfacing with offline storage. 3. The PEEK and POKE programs in "Customize Your HP-28" work on the HP-28S as well as on the HP-28C (that's why they were written in machine language - so they would be independent of ROM code changes), but on the HP-28S the command HOME should be included at the beginning of the PEEK and POKE programs so the machine code will not go into a subdirectory. As the top of RAM is now at #CFFFF, all three occurrences of #4FF in PEEK and POKE should be replaced by #CFF. 4. I shall be away for 3 weeks from March 7 to March 28, so I shall not be able to answer questions about the book. I'm sure the folks at Zengrange will carry on answering questions, and with luck we might even get some interesting answers from inside HP too. Anyone who has missed the information posted by Jurjen N.E. Bos would be well advised to go back and read it - fascinating stuff for the HP hackers among us. Many thanks to Jurjen for posting it. W.Mier-Jedrzejowicz, Ph.D., EARN/BITNET: MIER@SPVA.PHYSICS.IMPERIAL.AC.UK JANET: MIER@UK.AC.IMPERIAL.PHYSICS.SPVA UUCP: uunet!mcvax!ukc!spva.physics.imperial.ac.uk!mier Smail: Physics Dept, Imperial College, London SW7 2AZ, England Disclaimer: Neither my employer nor HP are to blame. As for me, I accept no responsibility for what use anyone might make of my ravings. Just the same, have fun!
bamcpherson@orchid.waterloo.edu (Brent) (03/24/88)
I am going to be buying an HP-28S (as soon as I get my tax return) and have read a few articles on the HP-28 line. Consequently I have a few questions about the HP-28: 1. I have heard mention of various books on customizing the HP-28. Where can these books be obtained? 2. What type of machine language does the HP-28 use and is there any documentation or books that describe the opcodes and their format (in hex)? 3. How is the screen memory organized and can it be written to? Also, is there several screen modes such as text and/or graphics? Excuse me if these questions sound stupid since I do not yet own an HP-28 and have not tried one. It sounds like it would be a great toy to hack around with. Thanks in advance... ;-) -- Brent
ccplumb@watmath.waterloo.edu (Colin Plumb) (03/24/88)
bamcpherson@orchid.waterloo.edu (Brent) wrote: > 3. How is the screen memory organized and can it be written > to? Also, is there several screen modes such as > text and/or graphics? On the 28S, there are commands to read and write a screen bitmap. It comes out as a 544-character string, where the first byte corresponds to the 8-pixel column at the start of the first text row, this continues across until the 137th byte corresponds to the 8-pixel column at the start of the second text row, etc., in the manner of sending bitmaps to a dot-matrix printer. You can use the logical operations (AND, OR, etc.) on such strings. You can also write arbitrary text to any of the 4 display rows, and make custom menus. There is only 1 display mode, bitmap. -- -Colin (watmath!ccplumb) Zippy says: Youth of today! Join me in a mass rally for traditional mental attitudes!
Jake_G_Schwartz@cup.portal.com (03/26/88)
Answering some of your questions....
1. There is only one text on the HP28 advanced applications, and I don't
think it
s out in the U.S. yet, but it may be available thru EduCalc Mail Store in
California (714-582-2637). It is from England and is 100 pages on many
HP28C and S features beyond the beginner stuff. This includes PEEK and
POKE, machine code, advanced SYSEVAL functions and hardware mods. Of
course, there is the book "An Easy Course in the HP28C" by Grapevine
Publications, but it really for beginners only. It isrumored that an
excellent book may be released very soon on the HP28C/S from an HP
employee with more valuable information as well.
2. The machine language of the HP28 is virtually the same as that of the
HP71 handheld computer, released in 1984 and still on the market today. This
processor, codenamed Saturn, is a 4-bit device running at 1 MHz in the 28S.
There is much documentation on the HP71 available to the public, for around
$200.00 for the whole lot (over a foot of stuff!) also from Educalc, but
no internal stuff on the 28C/S. But, of course, it is a closed machine, any-
way. One gentleman (Jurjen Bos in Holland) is disassembling the 28C ROMs,
however, and was through 8Kbytes out of the 128K, last I heard from him. The
HP71 stuff is the only good documentation on this processor. However, there
are several people in the US HP Users' Group HPX (Handheld Program Exchange)
which exchange information in this area frequently. Brian Walsh heads up this
group. He can be reached for more information in Atlanta, GA at 404-391-0367.
The HPX address is P.O. Box 566727 Atlanta, GA 30356.
3. There is graphics mode as well as text mode on the 28C/S. Graphics may be
controlled in many ways for convenient plotting. In addition, the PIXEL
function allows one to turn on any dot in the 32 by 137 display. Full screens
may be saved as 548-byte string objects for later retrieval and use.
Jake Schwartz
135 Saxby Terr.
Cherry Hill, NJ 08003
609-751-1283 (home)