Path: utzoo!attcan!uunet!mcvax!enea!kth!draken!tut!santra!kaira!t31662k
From: t31662k@kaira.hut.fi (Andreas Gustafsson)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Still more on reading from the parallel port
Summary: There are 5+4 inputs
Message-ID: <18932@santra.UUCP>
Date: 23 Jan 89 19:55:27 GMT
References: <823@ttrde.UUCP>
Sender: news@santra.UUCP
Reply-To: gson@hupu.hut.fi (Andreas Gustafsson)
Organization: Helsinki University of Technology, Finland
Lines: 14

According to the IBM XT Techical Reference Manual the four command
lines in the printer adapter have open-collector drivers with 4.7k
pullup resistors, although the eight data lines have push-pull
drivers.  This means you should actually be able to use a total of 9
lines as inputs: the five status lines and the four command lines
(which should be written as all ones when used as inputs).  Note,
however, that the status and command bits are at different port
addresses and some of the bits are inverted... 

--
Andreas Gustafsson
Internet: gson@hupu.hut.fi
UUCP: ...uunet!mcvax!santra!hupu!gson
Voice: +358 0 563 5592