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From: PHYS169@canterbury.ac.nz (Mark Aitchison, U of Canty; Physics)
Newsgroups: comp.sys.ibm.pc
Subject: Re: INPUT PARALLEL DATA OVER THE PRINTER PORT?
Message-ID: <7811@canterbury.ac.nz>
Date: 1 Jun 90 15:43:42 GMT
Article-I.D.: canterbu.7811
References: <12548@netcom.UUCP> <3260@galena2.UUCP> <7730@canterbury.ac.nz> <1990May30.153755.29766@ux1.cso.uiuc.edu>
Lines: 24

In article <7730@canterbury.ac.nz> CHEM194@canterbury.ac.nz (J.DAVIS) writes:
>"input from address 03bch ( for mono graphics/printer adaptor ) or
>                    0378h ( for printer card )
> 
> this instruction gets data from the pins on the adaptor on to
> the data bus in a similar way to the out instruction on the 
> same adress"
> 
>Sure looks like fully bi-directional 8-bit to me ....
 
In article <1990May30.153755.29766@ux1.cso.uiuc.edu>, mjw06513@uxa.cso.uiuc.edu (Mary Winters) writes:
> It might at first glance, but if you actually try it, you'll find that you'll
> only be able to read the value last written to that register, not the value of
> some external signal applied to the output lines. That is, unless you remove
> the ground connection on pin 1 of U4 and tie this pin to +5V, thereby
> converting the output port into an input port.
> 
The answer is, in fact, *some* parallel printer ports allow 8-bit data input,
and some don't! Because of the risks in connecting data to a port that doesn't,
put resistors in series when trying it, e.g. 470 ohm. These will slow the
transfer rate, so you will want to take them out later.  Alternatively use the
handshaking pins for 4-bit transfer. 

Mark Aitchison.