109 lines
3.4 KiB
Groff
109 lines
3.4 KiB
Groff
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.\" Copyright (c) 1997
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.\" Michael Smith
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS''
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.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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.\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $Id$
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.\"
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.Dd January 2, 1998
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.Dt PPI 4
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.Os FreeBSD
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.Sh NAME
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.Nm ppi
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.Nd
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user-space interface to ppbus parallel 'geek' port
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.Sh SYNOPSIS
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.Cd "device ppi0 at ppbus?
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.sp
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Minor numbering: Unit numbers correspond directly to ppbus numbers.
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.Sh DESCRIPTION
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The
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.Nm
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driver provides a convenient means for user applications to manipulate the
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state of the parallel port, enabling easy low-speed I/O operations without
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the security problems inherent with the use of the
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.Pa /dev/io
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interface.
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.Sh PROGRAMMING INTERFACE
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.Pp
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.Fd #include </sys/dev/ppbus/ppi.h>
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.Fd #include </sys/dev/ppbus/ppbconf.h>
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.Pp
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All I/O on the
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.Nm
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interface is performed using
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.Fn ioctl
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calls. Each command takes a single
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.Ty u_int8_t
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argument, transferring one byte of data. The following commands are
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available:
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.Bl -tag -width 10
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.It PPIGDATA, PPISDATA
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Get and set the contents of the data register.
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.It PPIGSTATUS, PPISSTATUS
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Get and set the contents of the status register.
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.It PPIGCTRL, PPISCTRL
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Get and set the contents of the control register.
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The following defines correspond to bits in this register. Setting
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a bit in the control register drives the corresponding output low.
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.Bl -tag -width 10 -compact
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.It STROBE
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.It AUTOFEED
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.It nINIT
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.It SELECTIN
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.It PCD
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.El
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.It PPIGEPP, PPISEPP
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Get and set the contents of the EPP control register.
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.It PPIGECR, PPISECR
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Get and set the contents of the ECP control register.
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.It PPIGFIFO, PPISFIFO
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Read and write the ECP FIFO (8-bit operations only).
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.El
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.Sh EXAMPLES
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To present the value 0x5a to the data port, drive STROBE low and then high
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again, the following code fragment can be used:
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.Bd -literal -compact
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int fd;
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u_int8_t val;
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val = 0x5a;
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ioctl(fd, PPISDATA, &val);
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ioctl(fd, PPIGCTRL, &val);
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val |= STROBE;
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ioctl(fd, PPISCTRL, &val);
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val &= ~STROBE;
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ioctl(fd, PPISCTRL, &val);
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.Ed
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.Sh BUGS
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The inverse sense of signals is confusing.
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.Pp
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The
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.Fn ioctl
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interface is slow, and there is no way (yet) to chain multiple operations together.
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.Pp
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The headers required for user applications are not installed as part of the
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standard system.
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