Measurement Computing Analyzer488 - Manual (Page 34)

Section 2 Getting Started
2.12
Total events = events prior to trigger + trigger point + total after trigger
Total records = records prior to trigger + trigger point + total after trigger
2.4.6 Trigger System
Triggering may be used while recording bus events to either halt the
IEEE 488 bus or to stop recording after a specific bus event occurs. This
feature is especially useful if more than 32,768 bus events occur while
recording. By either stopping the IEEE 488 bus or disabling recording, the
trigger system ensures that bus events of interest will not be overwritten by
subsequent bus events.
To use the trigger system to record bus events, a trigger point (a
specific bus state) must first be defined. Also, the number of matches to
skip before recording, the number of events to delay after the specified
number of matches, the number of events to record after the delay, and a
trigger complete action must be specified.
The trigger system is enabled (armed) and disabled (disarmed) by a
command or keypress. The arming mechanism resets the trigger system
counters, the trigger output signal, and partially enables the trigger system.
However, if the recording system is not also enabled, bus events will be
ignored by the trigger system. When recording and triggering are both
enabled, the Analyzer488 will record bus events and monitor them for the
trigger event.
The trigger system is composed of five stages. These stages are
listed below and shown pictorally in the following flowchart:
1. The Match Pattern (State of Data and Bus Management lines)
2. The Number of Occurrences of the trigger Match Pattern (Match Count)
3. The Number of events to count after the specified number of occurrences
of the match pattern have been found. (Trigger Delay)
4. The Number of events to count after the Trigger Delay count is
decremented to zero. (Post Count)
5. The action of the Analyzer488 after the specified number of events have
been recorded (When Complete action)