Printer Interf ace HP DeskJet Printers
HP DeskJet Printers
The following information applies to HP DeskJet 500, 600 and 800 Series
printers.
Interface information for HP DeskWriter printers and Macintosh compatible
dual-port DeskJet printers such as HP DeskJet 850C, 855C and 870C may
be found under “Printer Interface/HP DeskWriter Printers.”
Cable and Connector Information
Recommended Interface Cables
HP Cable
Host Interface
HP IEEE-1284
Compliant Cable
HP IEEE-1284
Compliant Cable
Part Number Cable Length Cable Connectors
C2950A 2 Meters DB-25 Male to 36-Pin
Centronics Male
C2951A 3 Meters DB-25 Male to 36-Pin
Centronics Male
Interface Specifications
HP DeskJet printers communicate with computers through a single
IEEE1284-B parallel I/O interface connector. For more information about
interface connection and operation, see “DOS I/O Interface Description.”
Communication Modes and Supported Protocols
Category Specification
Interface Protocol IEEE-1284 Compatible
Communication Modes Available * Compatible (Centronics)
* Nibble
* ECP
Printer Interf ace HP DeskJet Printers
IEEE-1284 Interface Connector
IEEE-1284 Interface Port (DOS/MS Windows)
Pin
Number Source
1 Host nStrobe HostClk HostClk
2 Bi-Directional Data 1 (LSB)
3 Bi-Directional Data 2
4 Bi-Directional Data 3
5 Bi-Directional Data 4
6 Bi-Directional Data 5
7 Bi-Directional Data 6
8 Bi-Directional Data 7
9 Bi-Directional Data 8
10 Bi-Directional nAck PrtClk PeriphClk
11 Bi-Directional Busy PrtBusy PeriphAck
12 Bi-Directional PError AckDataReq nAckReverse
13 Bi-Directional Select Xflag Xflag
14 Host nAutoFd HostBusy HostAck
15
Continued on next page
Compatibility
Mode
Nibble
Mode
ECP
Mode
Printer Interf ace HP DeskJet Printers
IEEE-1284 Interface Port (DOS/MS Windows) (Cont.)
Pin
Number Source
16 Logic Gnd
17 Chassis Gnd
18 Peripheral Peripheral Logic High
19 Signal Ground (nStrobe)
20 Signal Ground (Data 1)
21 Signal Ground (Data 2)
22 Signal Ground (Data 3)
23 Signal Ground (Data 4)
24 Signal Ground (Data 5)
25 Signal Ground (Data 6)
26 Signal Ground (Data 7)
27 Signal Ground (Data 8)
28 Signal Ground
29 Signal Ground
30 Signal Ground
31 Host nInit nInit nReverseRequest
32 Peripheral nFault nDataAvail nPeriphRequest
36 Host nSelectLn 1284 Active 1284 Active
Compatibility
Mode
Nibble
Mode
(Perror, Select, nAck)
(Busy, nFault)
(nAuto Fd, nSelectLn, nInit)
ECP
Mode
Printer Interf ace HP DeskJet Printers
DOS I/O Interface Description
The IEEE-1284 standard defines a signaling method for bi-directional
parallel communications between hosts and printers or other peripheral
devices. This standard provides improved performance and bi-directional
(two-way) communication, allowing a new generation of "intelligent"
peripherals to talk and listen to the host device.
HP DeskJet printers have an IEEE 1284-B parallel I/O interface connector.
This interface adheres to the IEEE 1284-B parallel interface standard
which was derived from the earlier "Centronics®" interface. Firmware in HP
DeskJet printers support the following modes of operation through the
IEEE 1284-B parallel interface port:
Compatibility Mode
Nibble Mode
Extended Capabilities Port (ECP) mode
Printer drivers on host computers "negotiate" with the printer to switch from
one mode to another. If an error occurs while in Nibble or ECP mode, the
interface automatically reverts to Compatibility mode.
HP DeskJet printer drivers meet the IEEE 1284-B standard for Level 1
devices. Input receivers meet the standard for Level 2 devices. This allows
HP DeskJet printers to be connected to either a Level 1 or Level 2 host.
Level 1 devices drive the interface with 5 V TTL circuits. Their
requirements are consistent with pre-existing installed devices and they
can operate with any other Level 1 compliant device. Level 1 devices are
characterized by steady-state electrical specifications.
Level 2 devices use output drivers with 45-55 ohms output impedance and
TTL receivers with 0.2 V- 1.2 V hysteresis. Level 2 devices capitalize on
the transmission-line characteristics of the connecting cable, providing
faster data transmission.
Compatibility Mode
Compatibility mode is a unidirectional mode of operation in which data
flows from the host computer to the printer. It is the mode that has, in the
past, been called “Centronics.”
Printer Interf ace HP DeskJet Printers
Nibble Mode
Nibble mode is a unidirectional mode of operation in which data moves
from the printer to the host computer. HP DeskJet printers and most
computer hosts can operate in nibble mode. Hosts can switch back and
forth between compatibility and nibble modes, thus establishing limited twoway (bi-directional) communication. The host must place itself and the
printer into nibble mode to receive status from the printer. This type of bidirectional communication has previously been called “Bitronics.”
ECP Mode
ECP mode provides a true bi-directional link between the printer and the
host computer. HP DeskJet printers and most computer hosts can operate
in ECP mode. ECP mode, combined with the HP proprietary
communication protocol, allows the Remote Control Panel for DOS and the
HP DeskJet Status Monitor for MS Windows to receive and display status
information from the printer.
Printer Interface HP DeskWriter Printers
HP DeskWriter Printers
Cable and Connector Information
Recommended Interface Cables
Cable Type HP Cable Part Number Apple Cable Part Number
AppleTalk Network 92215N M2068
RS-422-A High-Speed
Clocked Serial
Interface Specifications
92215S M0197
HP DeskWriter printers have an 8-pin mini-DIN interface connector port.
This connector port is compatible with RS-422-A serial, AppleTalk, and
high-speed externally-clocked serial mode communication. The printer
automatically determines if it is connected to an AppleTalk network or
directly to a Macintosh printer port.
Communication Modes and Supported Protocols
Category Macintosh I/O Connector
Communication Modes RS-422-A High-speed Serial
AppleTalk (230.4 Kbaud)
Macintosh Protocols Serial Pacing Protocol (SPP)
AppleTalk Transaction Protocol (ATP)
AppleTalk Link Access Protocol (ALAP)
Datagram Delivery Protocol (DDP)
Echo Protocol (EP)
Name Binding Protocol (NBP)
Printer Access Protocol (PAP)
Routing Table Maintenance Protocol (RTMP)
Printer Interface HP DeskWriter Printers
RS-422 Interface Connector (8-pin Mini-DIN)
TxD+
RxD+
TxD-
RxDGround
HSKo or DTR
1
RS-422 Interface Port (AppleTalk)
Pin Number Interface Pin Name Interface Pine Description
1 DTR Data Terminal Ready Output Handshake
2 NC No Connection in Printer
(Do not connect to ground or any other pin)
3 TxD- Transmit Data Line
4 Ground Shield Ground
5 RxD- Receive Data Line
6 TxD+ Transmit Data Line
7 NC No Connection
8 RxD+ Receive Data Line
Note
HP DeskWriter printer interface ports conform to RS-422 and
cannot be configured to operate as RS-232-C.
Printer Interface HP DeskWriter Printers
Mac I/O Description
HP DeskWriter and HP DeskJet 800 series printers detect and monitor
which interface mode (serial or LocalTalk) is present, and automatically
switch to the appropriate protocol. The printers determine if they are
connected to a LocalTalk node by detecting the presence or absence of a
transformer at the interface connector port. (A transformer detected at the
interface connector indicates the printer is connected to an LocalTalk
network.) If the mode changes while the printer is on, the printer restarts.
HP DeskWriter printers are compatible with two Macintosh serial interface
modes:
RS-422-A (57.6 Kbaud)
Clocked
RS-422-A signals are modulated against an inverted copy of the modulated
signal (for example RxD- and RxD+). Data communication occurs by
sensing which line is more negative than the other. Sensing line polarity in
respect to an inverted signal is more immune to interference and noise
than to a signal compared to a common ground. The signal is also less
likely to degrade over longer cable distances.
If a serial connection is made and "clocked" mode is detected, the printer
switches from DTR mode (the default at power-up ) to SPP mode. The
printer selects a frequency for the clocking and clocks the DTR line at that
frequency.
In AppleTalk mode, the printer receives data in a synchronous serial bit
stream at 230.4 K bits per second and converts the data to parallel.
Note
The Macintosh I/0 connector is RS-422-A compatible. It is
not possible to use this port as an RS-232-C serial
interface port.
Loading...