Hans B Pufal wrote:
>
> Allison J Parent wrote:
>
> > The 8008 does not have memory mapped IO, there are distinct IO
> > instructions. It's not to say MM/io is not done. The PDP-11 memory
> > and devices are the same things and there are no specialized IO
> > instructions.
>
> > The altair...(8800 and 8800a) from the front pannel there is no way to
> > interrogate an port mapped IO device or write to it. You must do it with
> > a little code.
>
> But surely this is a limitation of the front panel not the processor.
> I/O bus cycles can (easily) be generated from an appropriately designed
> front panel.
>
> --
> Hans B. Pufal
Hi Hans:
Not when you cannot directly address the I/O port. It's similar to the
address for the I/O port being an 'indexed' instruction. And you don't
have two levels of address toggles on the front panel to use at the same
time.
Chuck
--
-----------------------------------------------------------
He, who will not reason, is a bigot; William Drumond,
he, who cannot, is a fool; Scottish writer
and he, who dares not, is a slave. (1585-1649)
While he that does, is a free man! Joseph P. 1955-
-----------------------------------------------------------
Chuck Davis / Sutherlin Industries FAX # (804) 799-0940
1973 Reeves Mill Road E-Mail -- cad_at_gamewood.net
Sutherlin, Virginia 24594 Voice # (804) 799-5803
Received on Tue Feb 24 1998 - 11:08:57 GMT