<hardware, standard> (GPIB, General-Purpose Interface Bus, HP-IB,
Hewlett-Packard Interface Bus) An 8-bit parallel bus common on test equipment.
The IEEE-488 standard was proposed by Hewlett-Packard in the late 1970s and has
undergone a couple of revisions. HP documentation (including data sheets and
manuals) calls it HP-IB, or Hewlett-Packard Interface Bus.
It allows up to 15 intelligent devices to share a single bus, with the slowest
device participating in the control and data transfer handshakes to drive the
speed of the transaction. The maximum data rate is about one megabit per second.
Other standards committees have adopted HP-IB (American Standards Institute with
ANSI Standard MC 1.1 and International Electro-technical Commission with IEC
To paraphrase from the HP 1989 Test & Measurement Catalog (the 50th Anniversary
version): The HP-IB has a party-line structure wherein all devices on the bus
are connected in parallel. The 16 signal lines within the passive
interconnecting HP-IB (IEEE-488) cable are grouped into three clusters according
to their functions (Data Bus, Data Byte Transfer Control Bus, General Interface
In June 1987 the IEEE approved a new standard for programmable instruments
called IEEE Std. 488.2-1987 Codes, Formats, Protocols, and Common Commands. It
works with the IEEE Standard Digital Interface for Programmable Instrumentation,
IEEE 488-1978 (now 488.1). HP-IB is Hewlett-Packard's implementation of IEEE
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