National Instruments NI PXIe-6672 Using the PXI Star Triggers, Choosing the Type of Routing

Chapter 3 Hardware Overview

Refer to the Choosing the Type of Routing section for more information

about the synchronization clock.

Note The PXI_Trig/PXI_Star synchronization clock is the same for all routing operations

in which PXI_TRIG <0..7> or PXI_STAR <0..16> is defined as the output, although the

divide-down ratio for this clock (full rate, first divider, second divider) may be chosen on

a per route basis.

Using the PXI Star Triggers

There are up to 17 PXI star triggers per chassis. Each trigger line

is ad edicated connection between the System Timing Slot and one other

slot. The PXIS pecification, Revision 2.1, requires that the propagation

delay along each star trigger line be matched to within 1ns. A typical upper

limit for the skew in most NI PXI chassis is 500 ps. The low skew of the

PXI star trigger bus is useful for applications that require triggers to arrive

at several modules nearly simultaneously.

The star trigger lines are bidirectional, so signals can be sent to System

Timing Slot from a module in another slot or from System Timing Slot to

the other module.

You can independently select the output signal source for each PXI star

trigger line from one of the following sources:

• PFI<0..5>

• PXI triggers<0..7> (PXI_TRIG <0..7>)

• Another PXI star trigger line (PXI_STAR<0..16>)

• Global software trigger

• PXI_Trig/PXI_Star synchronization clock

•CLKIN

Refer to the Using the PXI Triggers section for more information on the

PXI_Trig/PXI_Star synchronization clock.

Choosing the Type of Routing

The NIPXIe-667 2 routes signals in one of two ways: asynchronously or

synchronously. The following sections describe the two routing types and

the considerations for choosing each type.