National Instruments NI 5911 - Manual (Page 22)

Chapter 2 Hardware Overview
© National Instruments Corporation 2-11 NI 5911 User Manual
Multiple-Record Acquisitions
After the trigger has been received and the posttrigger samples have been
stored, the NI 5911 can be configured to begin another acquisition that is
stored in another onboard memory record. This is a multiple-record
acquisition. To perform multiple-record acquisitions, configure the
NI 5911 to the number of records you want to acquire before starting the
acquisition. The NI 5911 acquires an additional record each time a trigger
is accepted until all the requested records are stored in memory. You may
acquire up to 1024 records if your NI 5911 is equipped with 4 MB of
onboard memory, or 4096 records with 16 MB. Software intervention after
the initial setup is not required.
Multiple-record acquisitions can quickly acquire numerous triggered
waveforms because they allow hardware rearming of the digitizer before
the data is fetched. Therefore the dead time, or the time when the digitizer
is not ready for a trigger, is extremely small.
For more information on multiple-record acquisitions and dead time, see
the Making a Multiple-Record Acquisition section in Chapter 5, Tasks and
Examples, of your NI-SCOPE Software User Manual.
RTSI Bus and Clock PFI
The RTSI bus allows NI digitizers to synchronize timing and triggering on
multiple devices. The RTSI bus has seven bidirectional trigger lines and
one bidirectional clock signal.
You can program any of the seven trigger lines to provide or accept a
synchronous trigger signal. You can also use any of the RTSI trigger lines
to provide a synchronization pulse from a master device if you are
synchronizing multiple NI 5911s.
You can use the RTSI bus clock line to provide or accept a 10 MHz
reference clock to synchronize multiple NI 5911 devices.
PFI Lines
The NI 5911 has two digital lines that can accept a trigger, accept or
generate a reference clock, or output a 1 kHz square wave. The function of
each PFI line is independent. However, only one trigger source can be
accepted during acquisition.