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 command takes a single uint8_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;
	     uint8_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 multiple operations together.

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

BSD
								  January 2, 1998							       BSD