Device And Rtsi Clocks; Synchronizing Multiple Devices - National Instruments PXI-6031E User Manual

Chapter 8 Real-Time System Integration Bus (RTSI)

Device and RTSI Clocks

Note DAQCard and DAQPad devices do not interface to the RTSI bus.

Synchronizing Multiple Devices

E Series User Manual
Many E Series device functions require a frequency timebase to generate
the necessary timing signals for controlling A/D conversions, DAC
updates, or general-purpose signals at the I/O connector. This timebase is
also called the Master Timebase or Onboard Clock. Refer to the
Timebase Signal section of Chapter 5, Counters, for more information.
Most E Series devices can use either their internal 20 MHz or 100 kHz
timebase or a timebase received over the RTSI bus. The timebase can only
be routed to or received from RTSI 7, or the RTSI clock. The device
directly uses this clock source, whether local or from the RTSI bus, as the
primary frequency source. If you configure the device to use the internal
timebase, you also can program the device to drive its internal timebase
over the RTSI bus to another device that is programmed to receive this
timebase signal. The default configuration at startup is to use the internal
timebase without driving the RTSI bus timebase signal.
With the RTSI bus and the routing capabilities of the DAQ-STC, there are
several ways to synchronize multiple devices depending on your
application. NI recommends that you use a common timebase as the
MasterTimebase signal and share any common triggers in the application.
One device is designated as the master device and all other devices are
designated as slave devices.
The 20MHzTimebase on the master device is the MasterTimebase signal
for all devices. The slave devices pull this signal from the master device
across the RTSI Trigger 7 line. Slave devices also pull any shared triggers
across an available RTSI trigger line from the master device. When you
start all of the slave devices before starting the master device, you have
successfully synchronized your application across multiple devices.
For more information, refer to Synchronizing E Series Devices in the
NI-DAQmx Help or the LabVIEW 8.x Help.
8-4
Master
ni.com