VTI Instruments EX1000A, User Manual

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EX10xxA Triggering 67
In addition to a single-master/multiple-slaves configuration, the LXI Trigger Bus can be configured
in Wired-OR mode. This mode allows multiple instruments to bring an LXI Trigger Bus channel to
a “1” state. The channel will only go back to “0” when all instruments have released it. This is useful
if multiple instruments in parallel operation must all complete before another instrument can begin
its operations. Each channel is programmable as to whether it is in Wired-OR or Master-Slave mode.
When an LXI Trigger Bus channel is configured for Wired-OR mode, exactly one instrument on the
bus must provide a bias on the channel. This is what allows the channel to fall deterministically back
to a “0” state when all other devices release it. Each channel is programmable as to whether it will
provide the Wired-OR Bias when it is in Wired-OR mode. default selections:

Wired-OR mode is off

Wired-OR Bias mode is off
L
OCKING
By default, the EX10xxA allows unrestricted operation from multiple hosts, both through the web
page and instrument driver interfaces. While this offers a high level of user flexibility, there are
instances where protected operation is desirable, if not required. For these applications, the
EX10xxA can be “locked,” meaning that it will accept function calls from only the host IP address
that issued the lock function. With the EX10xxA in this mode, other host connections that attempt
to make calls will be denied.
By design, the locking mechanism is able to be overridden by a secondary host that issues a break
lock command. Thus, the lock provides a warning to other users that the unit is in a protected
operation state, but not absolute security. This allows for instrument recovery if the locking IP
address would become disabled.
Self-calibration requires the acquisition of a lock prior to its initiation.
T
RIGGERING
The EX10xxA supports a full function trigger model with a separate arm source and trigger source
event structure. For a complete explanation of the trigger model, see
Error! Reference source not
found. . In summary, an acquisition sequence is enabled with a trigger initialize command. Scanning
is then initiated upon the receipt of the programmed arm source event followed by the receipt of the
programmed trigger source event. Trigger and arm source events can be independently programmed
from a variety of sources including Immediate, Timer, Digital I/O, the LXI Trigger Bus, and LXI
alarms.
D
ATA
F
ORMAT
By default, the data returned during data retrieval is limited to the channel readings and the absolute
time of scan initiation. If enabled, the EX10xxA can also return the measured CJC temperatures and
the delta timestamp of each channel reading from the scan initiation time.
A
CQUIRING
D
ATA
In general, the acquisition and retrieval of data on the EX10xxA are conducted with discrete
commands that are often separated in time to a large degree. The EX10xxA utilizes a 14 MB FIFO
memory storage to buffer acquisition data prior to retrieval. This reading buffer is cleared upon
receipt of the trigger initialize command in preparation for reading storage. Then, upon fulfillment
of the programmed trigger model conditions, the EX10xxA initiates the scanning of the channel
configuration that is defined in the scan list. It continues scanning and storing the acquisition data
until the trigger and arm count quantities are reached or the acquisition is aborted. At that point,
scanning ceases, and the trigger model is returned to the INIT layer.