IEEE1284-B
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IEEE1284-B

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 36 pin CENTRONICS female
36 pin CENTRONICS female connector  at the printer
PinSignalAbbr.Source
1Data Strobe (low)STROBEComputer
2Data Bit 1 (LSB)D1Computer
3Data Bit 2D2Computer
4Data Bit 3D3Computer
5Data Bit 4D4Computer
6Data Bit 5D5Computer
7Data Bit 6D6Computer
8Data Bit 7D7Computer
9Data Bit 8 (LSB)D8Computer
10Acknowledge (low)ACKPrinter
11Busy (high)BUSYPrinter
12Paper End (high)PEPrinter
13Select (high)SELPrinter
14Supply Ground -
15Oscillator Transmit Printer
16Logical Ground -
17Chassis Ground -
18+5 Vdc+VPrinter
19Return Data Strobe -
20Return Data Bit 1 -
21Return Data Bit 2 -
22Return Data Bit 3 -
23Return Data Bit 4 -
24Return Data Bit 5 -
25Return Data Bit 6 -
26Return Data Bit 7 -
27Return Data Bit 8 -
28Return ACK -
29Return BUSY -
30Return Input Prime -
31Input Prime (low) Computer
32Fault (low)FAULTPrinter
33---
34---
35---
36---
STROBEActive low pulse used to transfer data into the printer.Pulse with must be between 0.5 and 500 microseconds for most printers.
ACKActive low pulse indicates that data has been received and the printer is ready to accept more. 
BUSYA high signal indicates that the printer cannot receive data. 
PEA high signal indicates that the printer is out of paper (Paper End) 
SELECT OUTA high signal indicates that the printer is on-line 
AUTO FEEDA low signal indicates to the printer that a line feed is required after each Carriage return.This signal is used as a ground line by some manufacturers.
OSCXTA 100-200 KHz signal used by true Centronics printers only. 
+5V+5VdcNot provided by all manufacturers
PRIMEA low signal resets the printer to its power-up state and the printer buffer is cleared 
FAULTA low signal indicates that the printer is in an off-line or error state 
LINE COUNTUsed by true Centronics printers only.Most of the time not used
LINE COUNTSee 34 
SELECT INA high signal indicates to the printer that a DC1/ DC3 code is valid.This signal is used by a few manufacturers
Host Logic HighA high signal indicates that the host is alive (turned on).Specific IEEE 1284 signal.
Peripheral Logic HighA high signal indicates that the peripheral (printer) is alive (turned on).Specific IEEE 1284 signal.

IEEE-1284 (officially known as 1284-1994, Standard Signaling Method for a Bidirectional Parallel Peripheral Interface for PCs) refers to a standard set by the Institute of Electrical and Electronic Engineers. It specifies, among other things, five modes of data transfer: standard (legacy style), reverse (nibble and byte modes), and half-duplex or bidirectional (EPP and ECP). It also details cable properties and connector types. The 1284 standard is an innovation that allows parallel printer ports to transfer data at many times the standard speed, and also allows for an array of bidirectional communications and longer cable runs. The Enhanced Parallel Port (EPP) and Extended Capabilities Port (ECP) both follow 1284 standards, although EPP was developed prior to 1284"s release. The primary advantage of this technology is the ability to use devices on a PC"s parallel port that were previously unable to be used because of communication limitations. However, printers have also benefited and Hewlett-Packard"s Bitronix protocol, introduced with their LasetJet 4, is proof. Bitronix takes advantage of 1284"s nibble mode, and allows data to be sent from the printer to the computer quickly in this manner.

What is the difference between an IEEE-1284 cable and a standard one?
This is often a misunderstood concept. First, let"s make the distinction between bidirectional and 1284-compliant cables. Applying the 1284 standard to cables, the IEEE-compliance primarily means speed, and these cables are precisely manufactured for that purpose. The 1284 standard sets exacting specifications on cable impedance, shielding, length, and connector styles to insure that they will be up to the task. Bidirectional cables must simply be able to transfer data in both directions, and your everyday 25-wire printer cables (and all straight-thru 25 wire cables) are capable of this; they are not, however, capable of the speed required by 1284-compliant peripherals. Peripherals which are IEEE-1284 compliant (such as many newer printers) require the use of a high-speed cable, as do most of the devices that connect to an EPP or ECP.

Describe the connectors that are used on these cables.
There are three official types of connectors: they are termed "A," "B," and "C." The "A" type is a standard DB25 and the "B" type is your typical Centronics 36 connector. The "C" type is exclusive to 1284, and is intended to be used on new equipment which conforms to the standard; it is called a half-pitch Centronics 36 connector (HPCN36).

What devices require IEEE-1284 cables?
As a rule of thumb, any device that requires your computer"s parallel port to be set to EPP/ECP mode is worthy of a 1284-compliant cable. Specifically, most newer printers, backup devices, scanners, and the like require these cables. In addition, any parallel device with an HPCN36 connector requires a 1284 cable. If in question, refer to the user"s manual of that specific device.

Can I use a non-1284 compliant cable instead of one that is?
It is possible, but not recommended. Results can range from limited success to complete lack of operation.

What are the length restrictions on cables? Do I need to terminate the end of the chain?
In order to maintain peak performance, the total distance from computer to the last device should be no more than about 35 feet. Longer runs may be utilized with a possible drop in overall performance. No external termination is required; peripherals already come with the necessary termination. At PC Cables and Parts, you"ll discover an easy to use, information packed web site. Click here to learn more about Printer Cables.

Note: Direction is Computer relative Device.

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