The IEEE 1284 standard, called "Signalling Method for a Bi-directional
Parallel peripheral Interface for Personal Computers", is used
for bi-directional parallel printer bus support. It defines two
interface levels; a physical and electrical interface.
The level 1 interface is for devices that need a reverse mode capabilities
but do not operate at high speeds. The level II interface is for
both bi-directional and high speed communications.
The 1284 standard also defines connectors for use in the parallel
interface. The 25 pin DB25 connector is defined as the type "A"
connector. The Telco 36, a 36 conductor, 0.085" centerline
Champ connector with bale locks, is defined as the type "B"connector.
The Type "C" connector is a 36 contact, 0.05" centerline
mini connector with clip latches.
Additionally, the IEEE 1284 standard specifies;
- All signals are twisted pair with a signal line twisted to its
- Each signal and ground return must have a characteristic impedance
of 62 ±6 ohms over the frequency band of 4 to 16 MHz
- The wire to wire crosstalk shall be no greater than 10%
- The cable will have shielding with a minimum of 85% optical
braid coverage over foil
- The cable shield shall attach to the connector back shell using
a 360° concentric method. A pigtail connection is not acceptable
- Complaint cable assemblies shall be marked: "IEEE std.