IEEE 1284 Cabling Guide

The "IEEE Std.1284-1994 Standard Signalling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers", is for the parallel port what the Pentium processor was to the 286. The standard provides for high speed bi-directional communication between the PC and an external peripheral that can communicate 50 to 100 times faster that the original parallel port. It can do this and still be fully backward compatible with all existing parallel port peripherals and printers.

The IEEE1284 standard defines 5 modes of data transfer. Each mode provides a method of transferring data in either the forward direction (PC to peripheral), reverse direction (peripheral to PC) or bi-directional data transfer (half duplex). The defined modes are:

Forward direction only

Reverse direction only

Bi-directional

IEEE 1284 CABLE ASSEMBLIES

In order to guarantee high performance operation, 10 Meter cable lengths, and interoperability among various platforms and peripherals, the 1284 standard defines the characteristics for the cable assemblies.

Contrary to popular belief, there is no such thing as a "standard" parallel printer cable. This typically refers to a cable assembly with a DB25 male on one end and a 36 pin Champ plug connector on the other end. Internally, the cables may have from 18 to 25 conductors, with 1 to 8 ground wires, they may have foil shielding and/or braid, and possibly a drain wire. With this type of assembly there is no way to control the cable impedance, crosstalk, capacitance and performance. This type of assembly is fine for operation at 10K bytes per second at 6 ft., but will not work reliably at 2M byte per second at 30 ft. cable lengths.

Some of the parameters for a compliant 1284 cable assembly include:

All signals are twisted pair with a signal and ground return

Each signal and ground return has a characteristic unbalanced impedance of 62 +/- 6 ohms over the frequency band of 4 to 16 MHz

The wire-to-wire crosstalk is to be no greater than 10%

The cable will have a minimum of 85% optical braid coverage over foil.

The cable shield shall be connected to the connector backshell using a 360 degree concentric method. A pigtail connection is not acceptable.

Compliant cable assemblies shall be marked with: "IEEE Std 1284-1994 Compliant"

Please refer to the 1284 standard for the complete list of requirements for a compliant cable assembly. The standard defines a number of different cable assembly configurations. For information on the various connector types, click here. The following is a list of the available assembly types.

A-A

A-B

A-C

B-C

On Bi-Tronic IEEE 1284 peripherals there are 3 different connections.

CABLE COMPLIANCE CRITERIA

Cable construction is very important for signal reliability and high speed communication. The IEEE 1284 specification clearly defines cable construction, electrical and signal characteristics. Custom built cables are not to be used with IEEE 1284 compliant devices unless they have been certified to be IEEE 1284 compliant. For highest reliability insure that all cables used with Bi-Tronic devices are IEEE 1284 compliant.

• Cable construction is very specific and hand wiring of a custom cable may NOT meet the IEEE 1284 compliance specifications.

• All cables that meet the IEEE 1284 criteria for compliance are clearly and permanently labeled IEEE 1284 to distinguish them from cables having the same connector types but different electrical characteristics.

• Non-compliant cables which are not marked as stated will not perform to the IEEE 1284 design specifications. Loss of data, host or peripheral lock-up, and intermittent operation may result.

All Hewlett Packard printers from 1996 models onwards comply to the IEEE 1284 standard. On some of these products, the Bi-directional function cannot be disabled. In practice this can create problems when trying to share a printer, or even connecting directly. Phone Suna if you are in doubt about the specification of any printer

It is essential to insure that the printer cable used is IEEE 1284 compliant.

BI-TRONIC / IEEE 1284 FAQ

Q: Will the original Centronics parallel host or peripheral operate correctly with an IEEE 1284 compliant device?

A: Yes. Compatibility Mode provides backward compatibility between old and new devices. In fact, reliability and performance may improve when using IEEE 1284 cables.

Q: How to tell if a host or peripheral is IEEE 1284 compliant ?

A: It will be clearly stated in the product documentation. If not contact the host or peripheral vendor.

Q: Operating the 1284-B connector/cable at distances greater than three meters (10 ft.).

A: Long distance bi-directional operation up to 10 meters, 32.8 ft. can be achieved. However manufacturers will only guarantee 3 Mtrs. Please contact Suna for more details and up to date information.

Q: Replacing an older parallel cable with an IEEE 1284 compliant cable, even if not experiencing problems today ?

A: There is no need to replace an older cable that is not causing a problem with the system. Replace them only if you are experiencing problems. HP recommends that all new products use the IEEE 1284 compliant cables. Also, when replacing older parallel cables, HP recommends using the new IEEE 1284 compliant cables.