Path: utzoo!mnetor!uunet!portal!cup.portal.com!Jake_G_Schwartz
From: Jake_G_Schwartz@cup.portal.com
Newsgroups: comp.sys.hp
Subject: Re: HP-28
Message-ID: <4131@cup.portal.com>
Date: 26 Mar 88 06:18:47 GMT
References: <12364@orchid.waterloo.edu>
Organization: The Portal System (TM)
Lines: 36
XPortal-User-Id: 1.1001.3676


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)