Newsgroups: comp.sys.ibm.pc
Path: utzoo!utgpu!tj
From: tj@gpu.utcs.utoronto.ca (Terry Jones)
Subject: Re: INPUT PARALLEL DATA OVER THE PRINTER PORT?
Message-ID: <1990May31.020814.26271@gpu.utcs.utoronto.ca>
Organization: UTCS Public Access
References: <12548@netcom.UUCP> <3260@galena2.UUCP> <7730@canterbury.ac.nz> <1990May30.153755.29766@ux1.cso.uiuc.edu>
Date: Thu, 31 May 90 02:08:14 GMT

The tech reference manual says that you read the value applied to the
parallel port ORed with what was last written to the port therefore if you
write 0 to the port you can read data. IT ALSO SAYS that you should NEVER
pull a port pin low (cause if 0 hasn't been written then the pin is high
and if you pull it low you FRY it!) therefore you should use tri-state or
diode isolated signals into the port.