Keithley 7002-HD User Manual page 59

4-28 Front Panel Operation Model 7002-HD User's Manual
In general, external triggers can be used as events to control scan operation. In
order for the Model 7002-HD to respond to external triggers, the appropriate layers
of scan operation must be properly configured. "Scan procedure" on page 4-13
explains how to program the three layers of the scan.
Asynchronous operation
The asynchronous mode uses separate lines for input and output triggers. For typ-
ical asynchronous Trigger Link operation, the channel layer of the scan is config-
ured with Channel Spacing set to TRIGLINK and Triggerlink Mode set to
Asynchronous. You must also select input and output lines for the channel layer.
Input and output triggers can be set to any of the six lines, but they cannot use the
same line. For example, if you select line #1 for input triggers, then output triggers
must use one of the other five lines (#2 through #6). During operation in the chan-
nel layer, each Trigger Link input trigger will close a channel in the scan. After the
relay settles, and the user programmed DELAY times out, the Model 7002-HD will
output a Trigger Link trigger (typically to a DMM to make a measurement). The
channel layer is configured using the CONFIGURE SCAN menu (see "Scan pro-
cedure" on page 4-13).
The scan layer and/or arm layer can also be programmed for TRIGGER LINK:
SCAN SPACING is set to TRIGLINK, and ARM SPACING is set to TRIGLINK.
When using Trigger Link in these layers, you must also select input and output
lines as you did in the channel layer. Keep in mind that you can use the same lines
in the scan and arm layers that you selected in the channel layer.
Semi-synchronous operation
In the semi-synchronous Trigger Link mode, all triggering (input and output) in the
test system is controlled by a single line. When the normally high (+5V) trigger line
is pulled low (0V), a trigger occurs on the negative-going edge. When the trigger
line is released, a trigger occurs on the positive-going edge (see Figure 4-7). The
advantage of this single line trigger is that as long as one of the instruments in the
system holds the line low, the trigger is suppressed. In other words, the trigger will
not occur until all instruments in the system are ready.
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