ieee1284_negotiate, ieee1284_terminate — IEEE 1284 negotiation
#include <ieee1284.h>
int ieee1284_negotiate( | port, | |
mode); |
struct parport * | port; |
int | mode; |
void ieee1284_terminate( | port); |
struct parport * | port; |
These functions are for negotiating to and terminating
from IEEE 1284 data transfer modes. The default mode is
called compatibility mode, or in other words normal printer
protocol. It is a host-to-peripheral mode only. There are
special modes that allow peripheral-to-host transfer as well,
which may be negotiated to using
ieee1284_negotiate. IEEE 1284
negotiation is a process by which the host requests a
transfer mode and the peripheral accepts or rejects it. An
IEEE 1284-compliant device will require a successful
negotiation to a particular mode before it is used for data
transfer (but simpler devices may not if they only speak one
transfer mode).
To terminate the special mode and go back to
compatilibity mode use
ieee1284_terminate.
These functions act on the parallel port associated with
port, which must be claimed.
With a device strictly complying to IEEE 1284 you will
need to call ieee1284_terminate in
between any two calls to
ieee1284_negotiate for modes other than
M1284_COMPAT.
M1284_COMPAT: Compatibility
mode. Normal printer protocol. This is not a
negotiated mode, but is the default mode in absence of
negotiation. ieee1284_negotiate(port,
M1284_COMPAT) is equivalent to
ieee1284_terminate(port). This
host-to-peripheral mode is used for sending data to
printers, and is historically the mode that has been
used for that before IEEE 1284.
M1284_NIBBLE: Nibble mode.
This peripheral-to-host mode uses the status lines to
read data from the peripheral four bits at a time.
M1284_BYTE: Byte mode. This
peripheral-to-host mode uses the data lines in reverse
mode to read data from the peripheral a byte at a
time.
M1284_ECP: ECP mode. On
entry to ECP mode it is a host-to-peripheral
(i.e. forward) mode, but it may be set to reverse mode
using ieee1284_ecp_fwd_to_rev(3). It is common
for PC hardware to provide assistance with this mode by
the use of a FIFO which the host (or, in reverse mode,
the peripheral) may fill, so that the hardware can do
the handshaking itself.
M1284_EPP: EPP mode. In this
bi-directional mode the direction of data transfer is
signalled at each byte.
M1284_FLAG_DEVICEID: Device
ID retrieval. This flag may be combined with a nibble,
byte, or ECP mode to notify the device that it should
send its IEEE 1284 Device ID when asked for
data.
M1284_BECP: Bounded ECP is a
modification to ECP that makes it more robust at the
point that the direction is changed. (Unfortunately it
is not yet implemented in the Linux kernel
driver.)
M1284_ECPRLE: ECP with run
length encoding. In this mode, consecutive data bytes
of the same value may be transferred in only a few
cycles.
The negotiation was successful.
Negotiation is not available with this port type.
Negotiation was rejected by the peripheral.
Negotiation failed for some reason. Perhaps the device is not IEEE 1284 compliant.
A system error occured during negotiation.
The port parameter is
invalid (for instance, perhaps the
port is not claimed).