[A83] Re: LD A,R ; LD R,A

To: assembly-83@lists.ticalc.org
Subject: [A83] Re: LD A,R ; LD R,A
From: Peter-Martijn Kuipers <hyper@hysoft-automation.com>
Date: Sat, 14 Jul 2001 18:37:39 +0200 (CEST)
In-Reply-To: <F214sGSaVkpCCuc5bWs0000394a@hotmail.com> from "Dan Weiss" at Jul 14, 2001 11:33:38 AM
Reply-To: assembly-83@lists.ticalc.org


Hmm, handy, a random register like that...
 
> 
> The Z80 has one anyway, and it's found on all [real] z80's.  Use it as the 
> 'random' register.  It's even more random when interrupts are enabled...
> 
> 
> >From: "Michael Vincent" <hookman@worldnet.att.net>
> >Reply-To: assembly-83@lists.ticalc.org
> >To: <assembly-83@lists.ticalc.org>
> >Subject: [A83] Re: LD A,R ; LD R,A
> >Date: Sat, 14 Jul 2001 09:29:38 -0700
> >
> >
> >The 83/83+/83+ SE all use a static RAM chip though. From the docs, "The
> >asynchronous and
> >static nature of the memory requires no external clock or refresh circuit."
> >I would think then that the R register wouldn't be needed?
> >
> >
> >Michael Vincent
> >Detached Solutions - www.detacheds.com
> >Radical Software - www.radicalsoft.org
> >
> >----- Original Message -----
> >From: <ComAsYuAre@aol.com>
> >To: <assembly-83@lists.ticalc.org>
> >Sent: Saturday, July 14, 2001 7:14 AM
> >Subject: [A83] Re: LD A,R ; LD R,A
> >
> >
> > > From "Programming the Z80" by Rodnay Zaks:
> > >
> > > "The R register is the memory-refresh register.  It is provided to 
> >refresh
> > > dynamic memories automatically.  Such a register has traditionally been
> > > located outside the microprocessor, since it is associated with the
> >dynamic
> > > memory.  It is a convenient feature which minimizes the amount of 
> >external
> > > hardware for some types of dynamic memories."
> > >
> > > Basically, the r register gets incremented each byte of instruction 
> >code.
> > > It's used in some pseudo-random number generators, such as ztetris, but 
> >it
> > > can't be used without some sort of variable-length delay between uses
> >(such
> > > as waiting for someone to hit a key), because otherwise the output won't
> >be
> > > very random.  Otherwise, it has little practical use on calculators.
> > >
> > >
> > > In a message dated 7/14/2001 2:44:27 AM Eastern Daylight Time,
> > > hyper@hysoft-automation.com writes:
> > >
> > >
> > > >
> > > > When using the tasm80.tab file, I
> > > > came upon the opcodes LD A,R and LD R,A
> > > > They have a '1' at the end of the line
> > > > (the class), so I guess they're four our
> > > > processor. But I'm curious as to that this
> > > > R means. It can't be meaning 'other registers'
> > > > since they're all taken care for elsewhere in the
> > > > table file. My guess is that it's a special system
> > > >
> > >
> > >
> > >
> > >
> > > ----
> > > Jonah Cohen
> > > <ComAsYuAre@aol.com>
> > > http://jonah.ticalc.org
> > >
> > >
> > >
> > >
> >
> >
> >
> 
> _________________________________________________________________
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> 
> 
>

References:

[A83] Re: LD A,R ; LD R,A

From: "Dan Weiss" <dwedit@hotmail.com>