Re: A85: Re: Z80 Hardware

To: List-Assembly-85 <assembly-85@lists.ticalc.org>
Subject: Re: A85: Re: Z80 Hardware
From: Keith Burzinski <tsk3000@prodigy.net>
Date: Mon, 15 Sep 1997 18:05:42 -0700
Organization: Prodigy Internet
Reply-To: assembly-85@lists.ticalc.org

> > I'm presently designing a Z80 micro-computer system.  But there are a
> > few things I don't really understand yet.  ;)  Mainly the ports.  Like,
> > if I do 'out (7),a', where does that go, and how does it get there??? 
> > Is it somehow attatched to the address bus?  And then it reads the byte
> > on the data bus?  How???  Help me!  :)
> 
> It'll send whatever byte is in register A.

I know this!  I need to know _HOW_ the byte in A is written to the
device connected to the port.  Is it sent through the data bus?

For example:  if I
     ld    $C0,a
     out   (7),a
it will write $C0 to the device on port 7 (in this case, the link
port).  But _HOW_ is that $C0 _ACTUALLY_ written to the link port??? 
_WHAT ACTUALLY_ changes the lines on the link port?  It can't just be
"wired into the processor".  It has to have a line driver of some sort,
and some device to actually READ the byte from the processor.  Remember,
SOMETHING has to read it; it just doesn't magically go there...  I need
to know, how does that device interface with the Z80 processor chip???

Reguards,
-- 
~Keith
TSK3000@Prodigy.Net
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