Agilent Technologies HP 82335, Инструкция по установке, Страница: 41 / 54

HP-IS
Fundamentals
Controllers, Talkers, and Listeners
Controllers, Talkers, and Listeners
To understand communication among devices, you should be familiar with
the concepts of controller, talker, and listener.
Controller
Two types of controllers are defined within an HP-m system: system
controller and active controller.
There must be a single system controller capable of taking control of the
interface at any time. The system controller has exclusive control over the
IFC and REN lines.
Each system also has one or more devices capable of being active controller
(sometimes referred to as controller-in-charge), although there may be only
one active controller at any given time. The active controller has the ability
to perform tasks such as establishing listeners and talkers, sending bus
commands. and perronning serial polls.
In
most systems, a single computer will be both the system controller and the
only active controller. Some non-system controller devices may request
service. indicating their desire to be active controller, in order to perform some
operation such as plotting data
or
directly accessing disk drives. The current
active controller may "pass control" to a requesting device to make it the
active controller.
In
other systems, a system controller may not be capable of
operating as non-active controller, and therefore no pass-control capabilities
will exist. Note that system controller capabilities may not be transferred.
An HP-IB system can be configured in one of three ways.
and
it affects the
transfer of data as described:
•
No controller. This mode of data transfer is limited to a direct transfer
between one device manually set to talk only, and one or more devices
manually set to listen only.
•
Single controller. In this configuration,
data
transfer can be from controller
to devices (Command or Data mode). from a device to controller (Data
mode only),
or
from a device to other devices (Data mode only).
• Multiple controllers. This mode of data transfer is similar to that of a single
controller. with the requirement that active conU'oller status be passable
from one controller
to
another. In this configuration, one cOnLroller must be
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