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/share/man/man4/ppi.4

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  1.\" Copyright (c) 1997
  2.\"      Michael Smith
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 26.\" $FreeBSD$
 27.\"
 28.Dd January 2, 1998
 29.Dt PPI 4
 30.Os
 31.Sh NAME
 32.Nm ppi
 33.Nd "user-space interface to ppbus parallel 'geek' port"
 34.Sh SYNOPSIS
 35.Cd "device ppi"
 36.Pp
 37Minor numbering: unit numbers correspond directly to ppbus numbers.
 38.Pp
 39.In dev/ppbus/ppi.h
 40.In dev/ppbus/ppbconf.h
 41.Sh DESCRIPTION
 42The
 43.Nm
 44driver provides a convenient means for user applications to manipulate the
 45state of the parallel port, enabling easy low-speed I/O operations without
 46the security problems inherent with the use of the
 47.Pa /dev/io
 48interface.
 49.Sh PROGRAMMING INTERFACE
 50All I/O on the
 51.Nm
 52interface is performed using
 53.Fn ioctl
 54calls.
 55Each command takes a single
 56.Ft uint8_t
 57argument, transferring one byte of data.
 58The following commands are available:
 59.Bl -tag -width indent
 60.It Dv PPIGDATA , PPISDATA
 61Get and set the contents of the data register.
 62.It Dv PPIGSTATUS , PPISSTATUS
 63Get and set the contents of the status register.
 64.It Dv PPIGCTRL , PPISCTRL
 65Get and set the contents of the control register.
 66The following defines correspond to bits in this register.
 67Setting a bit in the control register drives the corresponding output low.
 68.Bl -tag -width indent -compact
 69.It Dv STROBE
 70.It Dv AUTOFEED
 71.It Dv nINIT
 72.It Dv SELECTIN
 73.It Dv PCD
 74.El
 75.It Dv PPIGEPP , PPISEPP
 76Get and set the contents of the EPP control register.
 77.It Dv PPIGECR , PPISECR
 78Get and set the contents of the ECP control register.
 79.It Dv PPIGFIFO , PPISFIFO
 80Read and write the ECP FIFO (8-bit operations only).
 81.El
 82.Sh EXAMPLES
 83To present the value 0x5a to the data port, drive STROBE low and then high
 84again, the following code fragment can be used:
 85.Bd -literal -compact
 86
 87	int		fd;
 88	uint8_t		val;
 89
 90	val = 0x5a;
 91	ioctl(fd, PPISDATA, &val);
 92	ioctl(fd, PPIGCTRL, &val);
 93	val |= STROBE;
 94	ioctl(fd, PPISCTRL, &val);
 95	val &= ~STROBE;
 96	ioctl(fd, PPISCTRL, &val);
 97
 98.Ed
 99.Sh BUGS
100The inverse sense of signals is confusing.
101.Pp
102The
103.Fn ioctl
104interface is slow, and there is no way (yet) to chain multiple operations together.
105.Pp
106The headers required for user applications are not installed as part of the
107standard system.