From: kskalb@immd1.informatik.uni-erlangen.de (Klaus Kalb)
Subject: Re: About 512Kb, 128Kb, and xxxKb cards, and a question
Organization: CSD., University of Erlangen
Date: Wed, 7 Oct 1992 10:42:16 GMT

dougc@bert.cs.byu.edu (Douglas R. Cannon) writes:

Hi.

>Anyway, I don't care about all that, I'm concerned about address space,
>address registers, and the like.

>Here's what I understand:

<correct description deleted>

>Now, here's what I don't understand:

>I am not sure of what card Smith Corona makes, but here is what I think I know.
>There is a 256Kb card, right? 
Ja. Never heard of Smith Corona, anyway. TDS makes one.

>Does anyone know if this acts physically like two 128Kb cards?
Yes, it acts like two 128kB cards.  But these cards can't be in place
at the same time. 

>(i.e., port 1 is at #80000h, port 2 is at #C0000h, and the built-in RAM is
>at #70000h, then reconfigured to #F0000h to access the hidden ROM?)
No. You have the card in port1 with one of the two banks visible
and port2 is free. The other bank of the card is out of sight.

>There is a 512Kb card, right?
True. I own one.

>Well, for the life of me, I can't figure this one out.
>Is there anyone who is using a 512Kb RAM card in their HP48 right now?
Yes, I do. (Well, in fact right now I'm using this SUN Sparc here in front
of me and not the HP48 ;-)

>Does anyone have any idea how this is done?
The bankswitching cards from TDS come with a library (ID 803, Name SWITCH
size is 1286 bytes) that supplies functions to switch the banks.
Bankswitching is equivalent to physically change the card in the port
and normally needs a warm start (same as ON-C) afterwards.

The XLIBS of that lib are:
  BS1 Switch banks in the card in port 1 and trigger warmstart
  BS2 Switch banks in the card in port 2 and trigger warmstart
  BANKN: Switch banks without warmstart (dangerous)
  SEARCH: Search for something (I never had use for that one)
  BSVER: Mine says it is version 2.0 

Note that you are not allowed to swap out a bank containing the library
(there would be no way back) or a merged bank (the calc would crash).
The software detects this. Thus you need to store this lib
in port0 (or in the other port, if appropriate)

>Are there entire 128Kb segments that are switched in and out, and you can only
>address 256Kb of RAM at once?

Near miss. You can only address one bank (128kB) of your card at a time.
The other port is free (for any other cad (another 512kB card ?))

>I know it would be possible to get it to work with the right hardware and
>software, but it seems that it would be such a horrible hack that it couldn't
>possibly work real reliably. 

The TDS card and the software is reliable. The only thing the card  doesn't
like is touching the contacts (it doesn't have the shutter like the HP-cards).
It comes with special box for the card while it is not inside an HP48.
  
IMHO the best way to use these cards is as independend memory with
a merged 128kB card in the other port. Of course you could merge
a TDS card as well, but you have to free it before switching banks.
Merging one bank of a 512kB card isn't a bright idea, you see.

I have the 512kB card sitting in port1 (being write protected most of
the time) and a merged 128kB card in port2. 
That's why I prefer libraries to directories.
And the best thing is that I can restore my calc after a crash in less
then one minute without use of a PC. Did you ever fool around
with SysRPL while being far away from your backups ? 
  
>Anyway, there's a couple of questions I hope we can get some answers to.
>I am open to any and all discussion whether knowledgeable or not.

All of this has been answered before. It should really be placed in the
FAQ (or in the unFAQ ?)

-KK
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    Klaus Kalb     | mail :  IMMD1 / Martenstr. 3 / W-8520 Erlangen / Germany 
 Werch ein Illtum  | email:  kskalb@immd1.informatik.uni-erlangen.de   
------------------------------------------------------------------------------
From: akcs.jwtrav@hpcvbbs.cv.hp.com (John Wettroth)
Date: Thu, 8 Oct 1992 07:40:03 GMT
Subject: Re: HP48SX <-> HP95LX serial and IR communications
Message-ID: <2ad3db9b.1868.1comp.sys.hp48.1@hpcvbbs.cv.hp.com>