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PPI(4)			 BSD Kernel Interfaces Manual			PPI(4)

NAME
     ppi — user-space interface to ppbus parallel 'geek' port

SYNOPSIS
     device ppi

     Minor numbering: unit numbers correspond directly to ppbus numbers.

     #include <dev/ppbus/ppi.h>
     #include <dev/ppbus/ppbconf.h>

DESCRIPTION
     The ppi driver provides a convenient means for user applications to
     manipulate the state of the parallel port, enabling easy low-speed I/O
     operations without the security problems inherent with the use of the
     /dev/io interface.

PROGRAMMING INTERFACE
     All I/O on the ppi interface is performed using ioctl() calls.  Each com‐
     mand takes a single u_int8_t argument, transferring one byte of data.
     The following commands are available:

     PPIGDATA, PPISDATA
	     Get and set the contents of the data register.

     PPIGSTATUS, PPISSTATUS
	     Get and set the contents of the status register.

     PPIGCTRL, PPISCTRL
	     Get and set the contents of the control register.	The following
	     defines correspond to bits in this register.  Setting a bit in
	     the control register drives the corresponding output low.
	     STROBE
	     AUTOFEED
	     nINIT
	     SELECTIN
	     PCD

     PPIGEPP, PPISEPP
	     Get and set the contents of the EPP control register.

     PPIGECR, PPISECR
	     Get and set the contents of the ECP control register.

     PPIGFIFO, PPISFIFO
	     Read and write the ECP FIFO (8-bit operations only).

EXAMPLES
     To present the value 0x5a to the data port, drive STROBE low and then
     high again, the following code fragment can be used:

	     int	     fd;
	     u_int8_t	     val;

	     val = 0x5a;
	     ioctl(fd, PPISDATA, &val);
	     ioctl(fd, PPIGCTRL, &val);
	     val |= STROBE;
	     ioctl(fd, PPISCTRL, &val);
	     val &= ~STROBE;
	     ioctl(fd, PPISCTRL, &val);

BUGS
     The inverse sense of signals is confusing.

     The ioctl() interface is slow, and there is no way (yet) to chain multi‐
     ple operations together.

     The headers required for user applications are not installed as part of
     the standard system.

BSD				January 2, 1998				   BSD
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