NAME
cent — Centronics-compatible interface
DESCRIPTION
cent
is a simple, widely used communication protocol
most commonly associated with printers, plotters and scanners.
It is an eight-bit parallel data interface
with additional control signals from the host computer,
and status signals from the peripheral.
The
cent
interface driver does no character processing;
that is, it does not interpret the data
being transferred between computer and peripheral.
Therefore, all bytes sent to or received from a device
are handled without alteration.
The
cent
interface driver always operates in
raw mode;
therefore, any desired data interpretation
must be performed by a user program
(such as the ``lp'' spooler in conjunction with an appropriate model
file).
The
cent
driver supports six different handshake modes for data transfer.
The last four bits of the minor number
of the device special file specify the mode used.
The format of the device minor number is:
where each letter after the ``0x'' prefix represents a single
hexadecimal digit, as follows:
- II
Specifies the instance number of the centronic interface.
- 000
Always zero.
- A
Specifies the handshake mode.
The handshake modes are:
- mode 1
Automatic handshaking using both
ACK
and
BUSY.
Minor number format:
0xII0001.
- mode 2
Automatic handshaking using only
BUSY.
Minor number format:
0xII0002.
- mode 3
Bidirectional read/write used for ScanJet.
Minor number format:
0xII0003.
- mode 4
Stream mode.
Data is essentially transmitted to the peripheral
without any handshaking protocol.
Minor number format:
0xII0004.
- mode 5
Pulsed mode using both
ACK
and
BUSY
for automatic handshaking.
Similar to mode 1 except that the data strobe line, nSTROBE
is pulsed for a fixed amount of time by the sender, then released.
Minor number format:
0xII0005.
- mode 6
Pulsed mode, using only
BUSY
for automatic handshaking.
Similar to mode 1 except that the data strobe line, nSTROBE
is pulsed for a fixed amount of time by the sender, then released.
Minor number format:
0xII0005.
Modes 1 and 2 support most HP *Jet series printers
(LaserJet, DeskJet, QuietJet, etc.).
AUTHOR
cent
was developed by HP.
