24 Feb
1998
24 Feb
'98
8:47 a.m.
<> The Intellec MCS8i and the PDP11 (obviously, since all I/O is memory
<> mapped) do allow you to access I/O devices directly from the panel.
<
<...and the front panel on the Altair 8800b.
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.
Allison
24 Feb
24 Feb
10 a.m.
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 : <mailto:hansp@digiweb.com>
Comprehensive Computer Catalogue : <http://www.digiweb.com/~hansp/ccc/>
_-_-__-___--_-____-_--_-_-____--_---_-_---_--__--_--_--____---_--_--__--_
11:08 a.m.
Hans B Pufal wrote:
Allison J Parent wrote:
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
--
-----------------------------------------------------------
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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(a)gamewood.net
Sutherlin, Virginia 24594 Voice # (804) 799-5803
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 
2:53 p.m.
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