Date: Wed, 11 Nov 1998 17:24:25 -0500 From: "David E. Cross" <crossd@cs.rpi.edu> To: Phillip Salzman <psalzman@gamefish.pcola.gulf.net> Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: Kernel Hacking stuffs (Bidirectional Parallel Port) Message-ID: <Pine.SGI.4.05.9811111719200.2459-100000@o2.cs.rpi.edu> In-Reply-To: <Pine.BSF.4.05.9811111511260.20199-100000@gamefish.pcola.gulf.net>
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On Wed, 11 Nov 1998, Phillip Salzman wrote: > > Have you looked at the Parallel Port Bus info (ie, ppbus)? > > I was going to use this while creating a driver for my parallel > port scanner, but noticed it would require a more advanced knowledge of C > than I had at the time. > > -- > Phillip Salzman I had not looked at it until you mentioned it. It suffers the same problems that the lpt.c driver does. The way these drivers gain their bidirectional ability is by tying the status lines (ACK, BUSY, PE, ERROR, and 1 I forget) to the data lines, allowing 5 bits of data at a time, one of these bits is used as a framing signal (0x1x means high nibble is being transfered, 0x0x is the low nibble). Am I correct in thinking that 'modern' bidirectional ports and printers have 8 lines dedicated to carrying data in both directions? Or is this the only way it has ever been, and ever will be? -- David Cross To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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