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

To: assembly-83@lists.ticalc.org
Subject: [A83] Re: LD A,R ; LD R,A
From: "Dan Weiss" <dwedit@hotmail.com>
Date: Sat, 14 Jul 2001 11:33:38 -0500
Reply-To: assembly-83@lists.ticalc.org


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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Follow-Ups:

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

From: Peter-Martijn Kuipers <hyper@hysoft-automation.com>