PSI BOX Reference
IEEE 488 Introduction
device using the CONFIGURE or PPC with PPE commands.
Depending on the Parallel Poll Response the controller may take
a variety of actions, chosen by the user’s program.
During a parallel the configured IEEE devices put their
parallel poll status bit on the IEEE data lines. The PSI BOX
reads the data line and store the response in bytes 36-38 of the
IEEE control string.
These bytes hold a value between 0 and 255. Knowing
what parallel poll configure information has sent sent the user
can interpret the data accordingly.
In general, few devices have the ability to be configured to
respond to a parallel poll.
Device Clear and Device Trigger.
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The device clear commands are used to make all or some
devices reset themselves to an initial power on state. The actual
initial state depends on the particular devices function. Device
clearing is very useful when a device hangs or inadvertently is
placed in unresponsive mode. It is worth noting that not all
IEEE devices are capable of recognising and executing a device
clear command, check the devices manual.
The SDC, selective device, clear command can be used to
set individual devices to their initial condition whilst the DCL,
device clear, command sends all devices to that condition.
Depending on whether any parameters are given the
CLEAR command performs an SDC or a DCL command.
Many IEEE devices have the capability to be pre-
programmed to perform a given action. When several devices are
programmed in this way it may be necessary to have them
perform their individual actions simultaneously or in sequence.
The TRIGGER command can be used to instruct several devices
or an individual device to perform take a reading
Device trigger commands are often used in a test and
measurement system to apply a signal to a component and then
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