Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!ub!acsu.buffalo.edu
From: cloos@acsu.buffalo.edu (James H. Cloos)
Newsgroups: comp.sys.handhelds
Subject: Re: More about HP-28S
Keywords: Hewlett Packard, HP28S, hp28, hp28s, HP28; <--Will this do? ;)
Message-ID: <58265@eerie.acsu.Buffalo.EDU>
Date: 6 Feb 91 23:12:28 GMT
References: <1991Feb6.073911.25628@agate.berkeley.edu>
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In article <1991Feb6.073911.25628@agate.berkeley.edu> c60c-3ia@web-4d.berkeley.edu writes:
>
>Days ago, I posted an article asking questions about HP-28S.  There has 
>been a fews responses, which I truly appreciates.  Nevertheless, not all 
>of my questions are answered, possibly because many people 
>are no longer interested in HP-28S.  But before can afford 
>a HP-48SX in my next incarnation, I would like to use my HP-28S 
>to its full potential.  So I decide to give the following questions 
>another chance:
>[etc]

OK, here is some more info.

>3)  In one of the posted articles about HP internals, I remember seeing a 
>warning that says improper use of SYSEVAL can result in memory loss or even 
>hardware problem.  I do not know how the later is possible.
>[etc]

The hardware control registers are mapped in memory on the Saturn-based
handhelds.  (On the 48, these are ~100h, I forget where on the 28s, but the
internals documentation would mention that.)  If you poke bad data into
those registers, hardware dammage can occur.  One of these registers
controls (to what degree I do not know) the voltage for the display.  Too
much, and "meltdown" occurs.  This actually looks like the display is
melting (not the physical hardware, mind you), and sustaining this can
eventually cause damage to the display.  The problem w/ sysevals is that if
you try an address that is not an rpl object or prefixed machine code, or
even try a valid address but w/ invalid arguments, whatever happens could
include poking into the hardware control registers, thus the potential for
actual, physical damage.

This is onlt one example of what the registers control, there are others,
but again, the internals docs should tell you what you need to know.

>I appreciate you answers.

Naturally.  And the net appreciates your (plural) questions.
^- ;-) -^			^--really--^

Seriously, though, that's what usenet what created for, ja?

Oh, and for 28 stuff, check out gmuvax2.gmu.edu (via anonymous ftp)
in the hp28 directory.  Mget the files "processor*" and "rom*",
also, greb "speed" for setting the calculator's speed.  It's not the best
version to have floated about on the net, but it does get the job done.

-JimC
--
James H. Cloos, Jr.		Phone:  +1 716 673-1250
cloos@ACSU.Buffalo.EDU		Snail:  PersonalZipCode:  14048-0772, USA
cloos@ub.UUCP			Quote:  <>