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IEEE1284_CONTROL(3)                Functions               IEEE1284_CONTROL(3)

NAME
       ieee1284_read_control, ieee1284_write_control, ieee1284_frob_control,
       ieee1284_do_nack_handshake - manipulate control lines

SYNOPSIS
       #include <ieee1284.h>

       int ieee1284_read_control(struct parport *port);

       void ieee1284_write_control(struct parport *port, unsigned char ct);

       void ieee1284_frob_control(struct parport *port, unsigned char mask,
                                  unsigned char val);

       int ieee1284_do_nack_handshake(struct parport *port,
                                      unsigned char ct_before,
                                      unsigned char ct_after,
                                      struct timeval *timeout);

DESCRIPTION
       There are four control lines, three of which are usually inverted on
       PC-style ports. Where they differ, libieee1284 operates on the IEEE
       1284 values, not the PC-style inverted values. The control lines are
       represented by the following enumeration:

           enum ieee1284_control_bits
           {
             C1284_NSTROBE   = 0x01,
             C1284_NAUTOFD   = 0x02,
             C1284_NINIT     = 0x04,
             C1284_NSELECTIN = 0x08,
             /* To convert those values into PC-style register values, use this: */
             C1284_INVERTED = (C1284_NSTROBE|
                               C1284_NAUTOFD|
                               C1284_NSELECTIN),
           };

       These functions all act on the parallel port associated with port,
       which must be claimed.

       The current values on the control lines are available by calling
       ieee1284_read_control, and may be set by calling
       ieee1284_write_control.

       To adjust the values on a set of control lines, use
       ieee1284_frob_control. The effect of this can be expressed by: ctr =
       ((ctr & ~mask) ^ val); that is, the bits in mask are unset, and then
       those in val are inverted.

       The special function ieee1284_do_nack_handshake is for responding very
       quickly in a protocol where the peripheral sets nAck and the host must
       respond by setting a control line. Its operation, which relies on the
       host machine knowing which interrupt nAck generates, is as follows:
        1.  Set the control lines as indicated in ct_before.
        2.  Wait for nAck interrupt. If timeout elapses, return
           E1284_TIMEDOUT.
        3.  Set the control lines as indicated in ct_after.

       On Linux using the ppdev driver, this is performed by the device driver
       in the kernel, and so is faster than normally possible in a user-space
       library.

RETURN VALUE
       The return value of ieee1284_read_control, if non-negative, is a number
       representing the value on the control lines.

       Possible error codes for ieee1284_read_control:

       E1284_NOTAVAIL
           The control lines of this port are not accessible by the
           application.

       E1284_INVALIDPORT
           The port parameter is invalid (for instance, perhaps it is not
           claimed).

       Possible error codes for ieee1284_do_nack_handshake:

       E1284_OK
           The handshake was successful.

       E1284_NOTAVAIL
           This operation is not available on this port type or system. This
           could be because port interrupts are not available, or because the
           underlying device driver does not support the operation.

       E1284_INVALIDPORT
           The port parameter is invalid (for instance, perhaps it is not
           claimed).

AUTHOR
       Tim Waugh <twaugh@redhat.com>
           Author.

COPYRIGHT
       Copyright (C) 2001-2003 Tim Waugh

                                  09/18/2007               IEEE1284_CONTROL(3)
 

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Quelle: http://www.trinler.net/de/service/doc/linux/man.html?command=ieee1284_write_control
Gedruckt am: 11.12.2017 13:58 GMT+0100 (2017-12-11T13:58:24+01:00)