From owner-freebsd-hackers Wed Nov 11 14:36:37 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id OAA11823 for freebsd-hackers-outgoing; Wed, 11 Nov 1998 14:36:37 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from cs.rpi.edu (mumble.cs.rpi.edu [128.213.8.16]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id OAA11817 for ; Wed, 11 Nov 1998 14:36:35 -0800 (PST) (envelope-from crossd@cs.rpi.edu) Received: from o2.cs.rpi.edu (root@o2.cs.rpi.edu [128.113.96.156]) by cs.rpi.edu (8.9.1/8.9.1) with ESMTP id RAA04904; Wed, 11 Nov 1998 17:35:53 -0500 (EST) Received: from localhost (crossd@localhost) by o2.cs.rpi.edu (8.9.1a/8.9.1) with ESMTP id RAA03202; Wed, 11 Nov 1998 17:35:53 -0500 (EST) X-Authentication-Warning: o2.cs.rpi.edu: crossd owned process doing -bs Date: Wed, 11 Nov 1998 17:35:53 -0500 From: "David E. Cross" To: Mike Smith cc: Phillip Salzman , freebsd-hackers@FreeBSD.ORG Subject: Re: Kernel Hacking stuffs (Bidirectional Parallel Port) In-Reply-To: <199811112228.OAA05676@dingo.cdrom.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Wed, 11 Nov 1998, Mike Smith wrote: > There are several different (incompatible) ways of shifting > bidirectional data. > > The nibble mode you describe is the lowest common denominator. There's > also "true bidirectional" mode, where the 8 data lines are > open-collector outputs, so driving them high lets you listen to the > other end. Then there are the EPP 1.7 and EPP 1.9 modes, and ECP to > finish it all off. > > Ppbus either supports or will support all of these, depending on the > capabilities of your hardware. You can see the nibble and "true" modes > in action in the 'vpo' driver. Ahh, this is what I was looking for. I had looked in lpt.c and nlpt.c (from the ppbus device directory). I will check out 'vpo' now, thank you :) -- David Cross To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message