Synchronizing With Ni-Daq - National Instruments NI-CAN User Manual

Synchronizing with NI-DAQ

© National Instruments Corporation
series getting started manual for detailed information about the PXI-846x
series RTSI interface.
The RTSI bus allows you to synchronize a CAN board with multiple
National Instruments DAQ, IMAQ, or additional CAN boards in your
computer. The RTSI bus can also synchronize CAN bus events between
multiple CAN boards. The trigger lines on the RTSI bus provide a flexible
interconnection scheme between CAN boards as well as between National
Instruments DAQ, IMAQ, and CAN boards.
Recent advances in test applications, in the automotive industry for
example, have demanded tighter integration of DAQ and CAN
measurements. The physical quantity being measured by DAQ and CAN
devices must be done close together (synchronized in time) to correlate the
data. This synchronization can be done in software, but the latency of the
operating system introduces delays that may not be acceptable for some test
applications. National Instruments CAN DAQ boards are equipped with an
RTSI bus that allows routing of timing/trigger signals between them. In a
system coupled using the RTSI bus, a CAN or DAQ board can be the
Master driving the timing/trigger signals, while other DAQ or CAN boards
are Slaves to this timing signal and base their actions on this signal.
Because the RTSI timing signals are handled in hardware, the host software
running on the PC does not interact in the acquisition or transmission (other
than retrieving the data when it has being acquired or writing new data).
Before using RTSI between CAN and DAQ, you must decide which board
to use as the Master. NI-CAN software allows easy configuration of the
Network Interface or CAN Objects as a Master or Slave. Note that both
configurations can exist on the same board, but not on the same object.
The software attribute that configures the object as a Master or Slave is the
RTSI Mode. The following RTSI Modes are available in NI-CAN:
• Disable RTSI
• On RTSI Input—Transmit CAN Frame
• On RTSI Input—Timestamp RTSI event
• RTSI Output on Receiving CAN Frame
• RTSI Output on Transmitting CAN Frame
• RTSI Output on
ncAction
The second and third modes listed above configure the object (Network
Interface or CAN Object) as a Slave that takes an action on the RTSI signal.
call
1-15
Chapter 1 Introduction
NI-CAN User Manual