VTI Instruments EX1401, Руководство пользователя

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EX1401 Instrument Drivers 77
750 Hz. Note that the actual reading output rate is far less than the 1 kSa/s maximum rate. To achieve
the maximum output rate, the TRIG event source should be set to Immediate.
Start, Trigger and Arm events
There are three events that control the progress through the trigger model: The Start, Arm, and
Trigger events. Each of these events can be programmed independently to be activated from any of
the External Trigger, Digital I/O port, LAN events, Channel Analog Levels, and LXI alarms. In
addition, each event can be programmed to be Immediate, creating a permanent satisfaction of the
event monitor. Each event monitor can also be bypassed on command with the issuance of a
Software Start, Software Arm, or Software Trigger, as appropriate. The full list of sources includes:
•
Digital Sources:
o
Immediate
o
Software
o
ALARM0-1
o
EXT
o
DIO0-7
o
LAN0-7
•
Analog Sources:
o
CH1 to CH16
The Start event source can be any one of the Digital sources, and is always a Falling Edge event.
The Arm event source can be any combination of the Digital sources, via either a Boolean AND or
a Boolean OR of all enabled sources. Each enabled source can be a High Level, Low Level, Rising
Edge, or Falling Edge event.
The Trigger event source can be a combination of either any of the Digital or any of the Analog
sources, via either a Boolean AND or a Boolean OR of all enabled sources. Each enabled source
can be a High Level, Low Level, Rising Edge, or Falling Edge event. Analog and Digital trigger
sources cannot be enabled at the same time.
The Digital I/O port and the External Trigger monitor the digital hardware ports on the rear panel
of the instrument. An Arm or Trigger event can be controlled by any combination of the eight
channels of each port.
LAN Events are triggered through the eight LAN Event channels via Ethernet packets
(UPD/multicast or TCP messages). They are configured in a manner similar to the Digital I/O port.
These events can occur in “past time”, “now”, or “future time”. “Past time” events have an IEEE
1588 time that occurred in the past. These will cause data starting from the time indicated in the
packet to be marked for retrieval. But, if the instrument was not in the
WaitingForTrigger state at
the specified time, the packet will be ignored. “Now” events have a IEEE 1588 time of “0”,
indicating that the event will occur immediately after it is received. Because they have a time of “0”,
the event log will only identify when this event was received. “Future time” events have an IEEE
1588 time that has not yet occurred. Because these events occur in the future, they can be prepared
for and provide a better response time than either “past” or “now” events.
LXI alarms are specified by IVI 3.15, IVILxiSync specification. The LXI alarm will cause an event
based on IEEE 1588 time and always occur at the pre-programmed time. The alarm period can be
set for this event as well, allowing the LXI alarm to fire repeatedly at a defined interval.
NOTE: The extensive flexibility of the trigger model system permits the creation of very specialized trigger
conditions, which is a powerful application tool. However, it also permits the creation of trigger
conditions that would be very difficult to satisfy in practice. For example, if edge conditions are
specified on multiple digital hardware channels, the edges must occur within 25 ns of each other to
be recognized as having occurred simultaneously.