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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Linking, Modules, and Overlays
Message-ID: <2732.UUL1.3#5129@willett.pgh.pa.us>
Date: 8 May 91 02:52:11 GMT
Organization: (n.) to be organized.  But that's not important right now.
Lines: 25


 Date: 05-03-91 (10:47)              Number: 2091 of 2105 (Echo)
   To: BILL TRIFFET                  Refer#: 4171
 From: RAY DUNCAN                      Read: 05-04-91 (19:44)
 Subj: PC@ AND LPT2                  Status: PUBLIC MESSAGE
 Conf: FORTH (58)                 Read Type: GENERAL (+)

 PC! writes the value to a port.  Whether the value *stays* at the port
 or not depends on how the port is wired -- if the port has "latches" or
 "buffers" on the system I/O bus, the value you write will "stick" there.
 However many ports don't work that way, so you can't count on anything
 without knowing the exact hardware characteristics of the device you're
 talking to.  You should think of a port address as being like a memory
 address, only it's an address in a very small address space that is
 completely separate from the normal CPU address space.  The CPU sends a
 value to an address and it has no control over what happens at the other
 end.

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