Interface Connection And Bus Structure - HP 3478A Technical Manual

3478A
b. Listener: Devices which receive information
over the HP-IB, when they have been addressed. A
device may or may not be both a talker and a listener.
Calculators and computers are generally both a talker and
a listener (at different times).
c. Controller: The device that can specify which
device(s) on the bus is a talker or listener. There can be
two types of controllers, an Active Controller and a System
Controller. The Active Controller is the current controlling
device. The System Controller can, however, take control
of the HP-IB even if it is not the Active Controller. There
can also be only one Active Controller at a time, even if
several controllers are on the Bus.
A-14. HP-IB Messages
A-15. Different types of information can be passed
over the HP-IB to one or more devices. Some of this
information is in the form of messages, most of which can
be separated into two parts. One part can be classified as
the address portion specified by the controller and the
information that comprises the messages. The second
part can be classified as HP-IB management messages.
These message are comprised of twelve messages and
are called Bus messages.
a. Data: The actual information (binary bytes) sent
Figure A-1. Interface Connection and Bus Structure
by a talker to one or more listener. The information (data)
can either be in numeric form or a character string.
b. Trigger: The Trigger message causes the
listening device or devices to perform a device dependent
action when addressed.
c. Clear: The Clear message causes the listening
device(s) or all the devices on the HP-IB to return to their
predefined device-dependent state.
d. Remote: This message causes the listening
device(s) to switch from local front panel control to remote
program control when addressed to listen.
e. Local: This message clears the REMOTE
message from the listening device(s) and returns the
device(s) to local front panel control.
f. Local Lockout: This message prevents a
device operator from manually inhibiting remote program
control.
g. Clear Lockout and Set Local: With this
message, all devices are removed from the local lockout
mode and revert to local. The remote message is also
cleared for all devices.
A-2
TM 11-6625-3071-14