[A83] Re: LD A,R ; LD R,A
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[A83] Re: LD A,R ; LD R,A
Static memory is more expensive. That's all I know.
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 12:04 PM
Subject: [A83] Re: LD A,R ; LD R,A
>
> Isn't static memory better, then?
>
> What are the differences (pro's/ against's)
> of dynamic and static memory
>
>
> >
> > Dyamic memories must be updated or they lose their information. I
believe
> > standard PC memory is dynamic, requiring refresh cycles.
> >
> >
> > Michael Vincent
> > Detached Solutions - www.detacheds.com
> > Radical Software - www.radicalsoft.org
> >
> > ----- Original Message -----
> > From: "Henk Poley" <HPoley@DDS.nl>
> > To: <assembly-83@lists.ticalc.org>
> > Sent: Saturday, July 14, 2001 10:53 AM
> > Subject: [A83] Re: LD A,R ; LD R,A
> >
> >
> > >
> > > > Van: Peter-Martijn Kuipers <hyper@hysoft-automation.com>
> > > >
> > > > Does this mean that the R register can be freely used, or are there
> > > > other less obvious uses for?
> > >
> > > From AsmGuru (found the same info also on other places):
> > >
> > > <<Q-1: I AND R REGISTERS. What they do.
> > >
> > > I is the Interrupt page address register [..]
> > >
> > > R is the memory Refresh register. The Z-80 CPU contains a memory
refresh
> > > counter to enable dynamic memories to be used with the same ease as
static
> > > memories. Seven bits of this 8 bit register are automatically
incremented
> > > after each instruction fetch. The eight bits will remain as programmed
> > with
> > > the LD R,A instruction.>>
> > >
> > > So you can use the R register to 'store' something, but only if that's
one
> > > bit...
> > >
> > > <<The data in the refresh counter is sent out on the lower portion of
the
> > > address bus along with a refresh control signal while the CPU is
decoding
> > > and executing the instruction. The programmer can load the R register
for
> > > testing purposes, but this register is normally NOT used by the
> > programmer.
> > > During refresh, the contents of the I register are placed on the upper
8
> > > bits of the address bus.>>
> > >
> > > The last thing told here doesn't apply to the Ti's, they only have
stactic
> > > RAM.
> > >
> > > I don't really understand in what way the R register is usefull for
> > dynamic
> > > memories (nor what dynamic memories exactly are).
> > >
> > > Henk Poley
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>
References: