ieee1284_read_data, ieee1284_write_data, ieee1284_data_dir, ieee1284_wait_data — control the data lines
#include <ieee1284.h>
int ieee1284_read_data( | port); |
struct parport * | port; |
void ieee1284_write_data( | port, | |
dt); |
struct parport * | port; |
unsigned char | dt; |
int ieee1284_data_dir( | port, | |
reverse); |
struct parport * | port; |
int | reverse; |
int ieee1284_wait_data( | port, | |
| mask, | ||
| val, | ||
timeout); |
struct parport * | port; |
unsigned char | mask; |
unsigned char | val; |
struct timeval * | timeout; |
These functions manipulate the data lines of the
parallel port associated with port
(which must have been claimed using ieee1284_claim(3)). The lines are represented by an 8-bit
number (one line per bit) and a direction. The data lines
are driven as a group; they may be all host-driven
(forward direction) or not
(reverse direction). When the
peripheral is driving them the host must not.
For ieee1284_data_dir the
reverse parameter should be zero to
turn the data line drivers on and non-zero to turn them off.
Some port types may be unable to switch off the data line
drivers.
Setting the data lines may have side effects on some port types (for example, some Amiga ports pulse nStrobe).
ieee1284_wait_data waits, up until
the timeout, for the data bits
specified in mask to have the
corresponding values in val.
ieee1284_read_data returns the
8-bit number representing the data lines unless it is not
possible to return such a value with this port type, in which
case it returns an error code. Possible error codes:
Bi-directional data lines are not available on this system.
The port parameter is
invalid (perhaps it has not been claimed, for
instance).
There was an error at the operating system level,
and errno has been set
accordingly.
The timeout has
elapsed.
Whereas ieee1284_read_data may
return E1284_NOTAVAIL on its first invocation on the port,
if it does not do so then it cannot until
ieee1284_close is called for that
port.