.\"	$OpenBSD: hpibbus.4,v 1.1 2008/04/01 14:22:28 jmc Exp $
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.Dd $Mdocdate: April 1 2008 $
.Dt HPIBBUS 4 hp300
.Os
.Sh NAME
.Nm hpibbus
.Nd HP-IB bus interface
.Sh SYNOPSIS
.Cd "hpibbus*	at nhpib?"
.Cd "hpibbus*	at fhpib?"
.Pp
.Cd "hd*	at hpibbus?                 " Pq "disks"
.Cd "ct*	at hpibbus?                 " Pq "cartridge tapes"
.Cd "mt*	at hpibbus?                 " Pq "9-track tapes"
.Cd "ppi0	at hpibbus? slave 5 punit 0 " Pq "plotter"
.Sh DESCRIPTION
HP-IB is essentially an IEEE 488 bus,
with an HP command set
.Po
CS/80 on
.Sq newer
devices, Amigo on before-the-early-1980s devices
.Pc
thrown on top.
Devices that respond to CS/80 (and probably Amigo, too)
are tagged with a 16-bit ID.
.Pp
HP-IB has a 2-level addressing scheme:
slave, the analog of a SCSI ID, and punit, the analog of a SCSI LUN.
.Pp
The CS/80 ID is unique to the slave, and is shared by all its punits.
Most devices only have one punit; multiple punits are often used for disk
drives that have an accompanying tape drive on the second punit,
or for dual floppy drives.
.Pp
In addition, not all HP-IB devices speak CS/80 or Amigo.
Examples of such devices are HP-IB plotters,
which simply take raw plotter commands over 488.
These devices do not have ID tags,
and often the host cannot even tell if such
a device is attached to the system.
.Sh SEE ALSO
.Xr \&ct 4 ,
.Xr hd 4 ,
.Xr intro 4 ,
.Xr nhpib 4 ,
.Xr ppi 4