From HwB

Developed by Hewlett-Packard, named Hewlett-Packard Instrument Bus (HP-IB). Later adopted by other manufacturers as GPIB (General Purpose Interface Bus). Become IEEE-488 in 1978.




24 PIN CENTRONICS FEMALE at the Devices.

Pin Name Description Source
1 DIO1 Data Bit 1 Talker
2 DIO2 Data Bit 2 Talker
3 DIO3 Data Bit 3 Talker
4 DIO4 Data Bit 4 Talker
5 EOI End Or Indentity Talker/Controller
6 DAV Data Valid Controller
7 NRFD Not Ready For Data Listener
8 NDAC No Data Accepted Listener
9 IFC Interface Clear Controller
10 SRQ Service Request Talker
11 ATN Attention Controller
12 Shield -
13 DIO5 Data Bit 5 Talker
14 DIO6 Data Bit 6 Talker
15 DIO7 Data Bit 7 Talker
16 DIO8 Data Bit 8 Talker
17 REN Remote Enabled Controller
18 Ground DAV -
19 Ground NRFD -
20 Ground NDAC -
21 Ground IFC -
22 Ground SRQ -
23 Ground ATN -
24 Logical Ground -



  • Max 15 devices on one bus
  • Max 20 m for all interconnected cables
  • Max speed 8000000 B/s

Data Lines

DIO=Data Input Output

Handshake Lines

DAV=Data Valid

Data Valid is a handshake line indicating that the active talker has placed data on the data lines.

NRFD=Not Ready For Data

Not Ready For Data is a handshake line indicating that one or more active listeners is not ready for more data. Note the active talker should then wait before sending any more data on the bus.

NDAC=Not Data Accepted

Not Data Accepted is a handshake line indocating that one or more active listeners has not accepted the current data byte. Note the active talker should leave the current byte asserted on the data lines until it has been accepted ot timed out.

Interface Management Lines


Attention is used primarily to differentiate between command mode and data mode. When ATN is TRUE (I.E. Active high) information on the bus is a command and when ATN is FALSE (Active LOW) the information on the bus is data.

IFC=Interface Clear

Interface Clear is under the exclusive control of the system controller. When it is active high all devices on the bus are returned to an idle state and the bus is cleared

REN=Remote Enable

Remote Enable may be set by the system controller to allow other devices to operate in remote mode.

SRQ=Service Request

Service Request can be set by a devive on the interface to indicate it is in need of service. SRQ could be set at the completion of a task. E.g. finished doing a measurement, or when an error as occurred.

EOI=End or Identify

End Or Indentify has two uses. EOI is asserted on the last byte of a data transfer. This signals all devices that no more data should be expected on the transfer.



  • IEC 60488-1:2004 (Old standard: IEC 60625-1:1993 / 625-1)
  • IEEE 488.1-2003
  • ANSI Standard MC 1.1
  • Old: IEEE Standard Digital Interface for Programmable Instrumentation, IEEE-488-1978