IEEE1284-B Parallel

The IEEE 1284-B connector is the 36-pin Centronics-style plug used on the peripheral side of IEEE 1284-compliant parallel cables between PCs and printers.

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IEEE1284-B Parallel – 36-pin connector 36 pin CENTRONICS female connector at the printer.

The IEEE 1284-B connector is the 36-pin, 0.085-inch pitch Centronics-style plug defined by IEEE 1284-2000 (first ratified as IEEE 1284-1994) for use on the peripheral — typically printer — end of a parallel cable. It carries the same 17 signal lines as the Type A DB-25 host connector: eight data lines, four control outputs from the host, and five status inputs from the peripheral, along with signal returns and power. The standard permits a maximum cable length of 25 feet and specifies a cable characteristic impedance of 62 ± 6 ohms. Pins 33–36 are unassigned in the IEEE 1284-B definition and are typically left unconnected.

PinDescriptionSignalSource
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 TransmitPrinter
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---

Notes

The 1284-B connector uses 0.085-inch pitch and is mechanically equivalent to the original Centronics 36-pin interface used on parallel printers since the 1970s; IEEE 1284 formalised its electrical and signalling requirements. The companion 1284-C connector uses a smaller 0.050-inch pitch (half-pitch MDR-36) and can serve both host and peripheral ends. Level II electrical specification (required for IEEE 1284 compliance): driver output VOH ≥ 2.4 V at 14 mA source current; VOL ≤ 0.4 V at 14 mA sink current; output impedance 50 ± 5 ohms; slew rate 0.05–0.40 V/ns. Receiver thresholds: VIH ≤ 2.0 V, VIL ≥ 0.8 V, hysteresis 0.2–1.2 V. Host and peripheral capability are negotiated via the IEEE 1284 negotiation sequence. Pins 33–36 are unassigned in the IEEE 1284-B definition.

Signals

  • STROBE — Active-low pulse from the host used to clock data into the printer; pulse width must be between 0.5 and 500 microseconds for most printers.
  • D1–D8 — Eight bidirectional data lines carrying one byte per transfer cycle.
  • ACK — Active-low pulse from the printer indicating that data has been received and the printer is ready to accept more.
  • BUSY — High signal from the printer indicating it cannot accept further data.
  • PE — High signal from the printer indicating a paper-out condition.
  • SEL — High signal from the printer indicating it is on-line and selected.
  • OSCXT — 100–200 kHz oscillator signal used by original Centronics printers only; not implemented by most later printers.
  • +5V — +5 Vdc supply; not provided by all manufacturers.
  • PRIME (nINIT) — Active-low signal from the host that resets the printer to its power-up state and clears the print buffer.
  • FAULT — Active-low signal from the printer indicating an off-line or error condition.
  • Host Logic High — IEEE 1284-specific signal indicating that the host is powered on; not present on the 1284-A (DB-25) connector.
  • Peripheral Logic High — IEEE 1284-specific signal indicating that the peripheral is powered on; not present on the 1284-A connector.

References

Category:Parallel Connectors