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

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


R is still incremented/altered though, so you couldn't store anything into
it. I don't know if it's used or not.


Michael Vincent
Detached Solutions - www.detacheds.com
Radical Software - www.radicalsoft.org

----- Original Message -----
From: "Peter-Martijn Kuipers" <hyper@hysoft-automation.com>
To: <assembly-83@lists.ticalc.org>
Sent: Saturday, July 14, 2001 9:26 AM
Subject: [A83] Re: LD A,R ; LD R,A


>
> Does this mean that the R register can be freely used, or are there
> other less obvious uses for?
>
> >
> > 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
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>
References: