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PPI(4)		      DragonFly Kernel Interfaces Manual		PPI(4)


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


device ppi Minor numbering: Unit numbers correspond directly to ppbus numbers.


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.


<dev/misc/ppi/ppi.h> <bus/ppbus/ppbconf.h> 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 PPIGEPPA, PPISEPPA Get and set the address bits of the EPP control register. PPIGEPPD, PPISEPPD Get and set the data bits 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).


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);


The inverse sense of signals is confusing. The ioctl() interface is slow, and there is no way (yet) to chain multi- ple operations together. DragonFly 5.1 January 2, 1998 DragonFly 5.1

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