IEEE1284_STATUS(3) Functions IEEE1284_STATUS(3)
ieee1284_read_status, ieee1284_wait_status - analyse status lines
int ieee1284_read_status(struct parport *port);
int ieee1284_wait_status(struct parport *port, unsigned char mask, unsigned char val,
struct timeval *timeout);
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:
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.
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:
The port lacks the required capability. This could be due to a limitation of this
version of libieee1284, or a hardware limitation.
Access to the status lines is not available on this port type.
The timeout has elapsed.
The port parameter is invalid (for instance, perhaps the port is not claimed).
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.
Tim Waugh <firstname.lastname@example.org>
Copyright (C) 2001-2003 Tim Waugh
[FIXME: source] 06/17/2014 IEEE1284_STATUS(3)