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IEEE1284_CONTROL(3)                Functions               IEEE1284_CONTROL(3)

       ieee1284_read_control, ieee1284_write_control, ieee1284_frob_control,
       ieee1284_do_nack_handshake - manipulate control lines

       #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);

       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|

       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

       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
        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

       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:

           The control lines of this port are not accessible by the

           The port parameter is invalid (for instance, perhaps it is not

       Possible error codes for ieee1284_do_nack_handshake:

           The handshake was successful.

           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.

           The port parameter is invalid (for instance, perhaps it is not

       Tim Waugh <twaugh@redhat.com>

       Copyright (C) 2001-2003 Tim Waugh

                                  09/18/2007               IEEE1284_CONTROL(3)

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Gedruckt am: 16.12.2017 04:18 GMT+0100 (2017-12-16T04:18:26+01:00)