Remote Operation Via Hp; Description Of The Hp; Capabilities Of The Hp - HP 3325B Operating Manual

Remote Operation via HP-IB
Description of the HP-IB
The HP-IB is a bus structure that links the HP 3325B to desktop computers, minicomputers,
and other HP-IB controlled instruments to form automated measurement systems. The
HP-IB is Hewlett-Packard's implementation of the IEEE Standard 488-1978 and ANSI
Standard MC 1.1,
All of the active HP-IB interface circuits are contained within the various HP-IB controlled
devices. The interconnecting cable is entirely passive and its role is limited to connecting the
devices in parallel so that data can be transferred from one device to another.
Every participating device must be able to perform at least one of the following roles; talker,
listener, or controller. A talker transmits data to other devices called listeners. Most devices
can be both a talker and listener, but not at the same time. A controller manages the
operation of the bus system by designating which device is to talk and which devices are to
listen at any given time. The HP 3325B can be either a talker or a listener.
The full flexibility and power of the HP-IB is realized when a controller is added to the
system. An HP-IB controller participates in the measurement by being programmed to
automate, monitor, and coordinate instrument operation as well as process the measurement
results. There may be raore than one controller on the bus but only one can be active at a
time. (Changing the active controller is accomplished with the
pass control
bus message.)
One (and only one) of the controllers should be hard-wired as the
system controller.
Capabilities of the HP-IB
Number of Interconnected Devices
Up to 15 devices, maximum, may be on one contiguous bus.
Interconnection Path/Maximum Cable Length
Star or linear bus network. Total transmission path length = 2 meters times number of
devices, or 20 meters, whichever is less, with a maximum of 3 meters separating any two
devices.
Message Transfer Method
B
3
h;e-serial, 8 bit-parallel, asynchronous data transfer using a 3-wire handshake.
Data Transfer Rate
One megabyte per second (maximum) over limited distances; actual data rate depends upon
the capability of the slowest device involved in the transmission.
Address Capability
Primary addresses: 31 talk, 31 listen; secondary (2-byte) addresses: 961 talk, 961 listen.
1 talker and 14 listeners, maximum, at one time. The HP 3325B has only primary address
capability. Table 2-2 lists the talk and listen HP-IB addresses.
2-2