IEEE1284_STATUS

Section: Functions (3)
Updated: 07/26/2009
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NAME

ieee1284_read_status, ieee1284_wait_status - analyse status lines

SYNOPSIS

#include <ieee1284.h>

int ieee1284_read_status(struct parport *port);
int ieee1284_wait_status(struct parport *port, unsigned char mask, unsigned char val, struct timeval *timeout);

DESCRIPTION

There are five status lines, one of which is usually inverted on PC-style ports. Where they differ, libieee1284 operates on the IEEE 1284 values, not the PC-style inverted values. The status lines are represented by the following enumeration:

enum ieee1284_status_bits
{
  S1284_NFAULT = 0x08,
  S1284_SELECT = 0x10,
  S1284_PERROR = 0x20,
  S1284_NACK   = 0x40,
  S1284_BUSY   = 0x80,
  /* To convert those values into PC-style register values, use this: */
  S1284_INVERTED = S1284_BUSY,
};

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

The purpose of ieee1284_wait_status is to wait until particular status lines have specified values. Its timeout parameter may be modified on return.

RETURN VALUE

For ieee1284_read_status, the return value is a non-negative integer with bits set as appropriate representing the status lines. A negative result indicates an error.

For ieee1284_wait_status, the return value is E1284_OK if the status lines now reflect the desired values (i.e. status & mask is val), or a negative result indicating an error.

Possible error codes:

E1284_NOTIMPL

: The port lacks the required capability. This could be due to a limitation of this version of libieee1284, or a hardware limitation.

E1284_NOTAVAIL

: Access to the status lines is not available on this port type.

E1284_TIMEDOUT

: The timeout has elapsed.

E1284_INVALIDPORT

: The port parameter is invalid (for instance, perhaps the port is not claimed).

NOTES

The nAck pin is often able to trigger interrupts on the host machine. With operating system help these interrupts may be visible to the application via the file descriptor returned by ieee1284_get_irq_fd.

Under Linux, the conditions are that the parallel port driver knows which interrupt line to use and is using it, and that the relevant /dev/parport device node is accessible and backed by a device driver.

AUTHOR

Tim Waugh <twaugh@redhat.com>

: Author.