Chassis Triggers

Trigger management provides a systematic way for multiple applications to share the backplane trigger lines without interfering with each other.

For example, let us say that Application A uses backplane trigger line 0 to send a trigger signal from the slot 2 module to the slot 3 module. Application B needs to send a signal from the slot 4 module to the slot 5 module. Obviously, it wouldn’t work well if Application B tried to use trigger line 0, because the slot 5 module would receive trigger signals generated by Application A’s slot 2 module. And Application B’s use of trigger line 0 would likewise confuse Application A’s slot 3 module. Such resource contention would interfere with the applications, but would also create the possibility of damaging the trigger drive hardware when two devices apply a signal to the trigger line. See the CAUTION below.

PXI-9 compliant trigger managers provide a way for applications, including Connection Expert, to dynamically query to see if a trigger line is used, and if not, reserve it for use by that application before trying to send signals on it. In this way, multiple applications can coordinate their use of the shared chassis trigger resources. It is the application programmer's responsibility to ensure that all applications requiring trigger resources call a trigger manager to secure reservations and routes for each client, and afterward, configure the instrument module drivers properly so that only a single trigger source is driving any configured trigger line.

Additionally, some chassis backplanes offer trigger lines that don’t span the entire backplane, but instead are split into two or three trigger bus segments (for example, the KeysightM9018 and M9019 18-slot PXIe chassis), requiring the chassis to route triggers from one trigger bus segment to another. This route is configurable. Applications that don’t coordinate their use of trigger bus routes can get into the problems described above. Trigger management provides a way for applications to manage both trigger reservations and routes between trigger bus segments.

Trigger Bus Segments: Smaller PXI chassis (usually 6 slots or less) generally have the backplane trigger lines running contiguously, without interruption, to all slots. For example, the Keysight M9005A 5-slot PXIe chassis has one trigger bus across all five slots. Larger chassis break the span of the trigger lines into multiple slot regions called trigger bus segments. The M9010A 10-slot chassis has two segments. The Keysight M9018A/B and M9019A PXIe chassis have three trigger bus segments. AXIe chassis have only one Trigger Bus Segment.

In the case of the Keysight 18-slot M9018A/B and M9019A chassis, slots 1 through 6 are in bus segment 1, slots 7 through 12 are in bus segment 2, and slots 13 through 18 are in bus segment 3. The following graphic shows the eighteen chassis slots grouped into three distinct trigger bus segments (labeled Bus 1, Bus 2, and Bus 3):

Chassis with two or more bus segments are called multi-segment chassis. A multi-segment chassis breaks the continuity of a trigger line between each bus segment.

Trigger Bus Reservations: PXI and AXIe chassis have trigger lines that are available to all of the cards in a chassis. Application may need to reserve one or more of the trigger lines, permanently or for a fixed time, for use by that application only. This is a trigger bus reservation. Trigger Bus Reservations can exist one only one Trigger Bus Segment, or if a Route is set up, the reservation may exist across two or more segments.

Trigger Bus Routes: Trigger lines in bus segments are independent unless the trigger lines are explicitly connected between segments. This connection is a trigger bus route. For example, if you connect trigger bus 5 on bus segment 1 to bus segment 2, you have "routed" the trigger bus line.

The chassis backplane includes repeaters to route a signal across a bus segment boundary. When the repeater is activated, via configuration, it enables modules on one bus segment to source trigger signals routed to another bus segment. In many chassis, the repeaters can make connections between bus segments in either direction, but not both directions at the same time (on a single trigger line) – so one repeater allows a signal to be routed from bus segment 1 to bus segment 2, and another repeater is used to route the other direction from bus segment 2 to bus segment 1. With three trigger bus segments, there are eight possible trigger bus routes. In the following graphic, there are eight trigger bus lines, each line showing a different trigger bus route. All of these route combinations may be applied to any of the eight trigger lines. The red text on the right of the trigger line numbers indicate the driver code to create that Trigger Bus route.

Before creating a route, you must reserve the destination segment, and preferably both the source and destination segments (as shown above). A reservation has a name called the client label that associates it with an application; KeysightConnection Expert's client label is Keysight_Persistent. See below for instructions on making reservations and routes.

Trigger Bus Routes between bus segments are not bidirectional. The repeaters make connections between bus segments in either direction, but not both directions at the same time (on a single trigger line)

Some multi-slot PXI instruments , such as the Keysight M9381A PXIe Vector Signal Generator, use peer-to-peer (module-to-module) triggering to function. If you install these modules on the same trigger bus segment, no routes are needed (but you should reserve the trigger line within a segment). But if you install them on different trigger bus segments, you must configure the trigger route and reserve the trigger line in both segments).

Connection Expert's Chassis Triggers view provides a graphical user interface for prototyping and troubleshooting trigger routes and reservations. In this view, you can reserve trigger lines in connected chassis, create trigger routes, and view routes and reservations created by other applications. Be aware that other applications may be depending on reservations and routes, and likely will not function correctly if you change them. Further, there is the possibility of damaging the trigger drive hardware if two devices apply a signal to the same trigger line. See the CAUTION below.

The Chassis Triggers view is not a trigger manager itself, but relies on underlying PXI-9 Trigger Manager API to implement trigger reservations and routing. Most chassis ship with their own vendor-supplied PXI-9 compliant trigger manager, but if a chassis does not have its own specific trigger manager, a default trigger manager will be used (installed with IO Libraries Suite). You can specify a default trigger manager in Connection Expert by selecting , then Settings, then PXI system options.

The PXI-9 PXI and PXI Express Trigger Management Specification (available on the PXI Systems Alliance Web site) defines a standard API for reserving backplane trigger lines and subsequently routing to them. This is done using a database that all applications share to avoid interfering with each other. This standard enables Connection Expert to operate non-Keysight chassis as well as Keysight chassis.

Keysight's KtMTrig IVI driver (installed with the Keysight PXIe Chassis Family Driver version) is an IVI driver wrapper for the generic trigger manager that provides programmatic control of trigger management for Keysight chassis. It provides a way for applications to share the backplane trigger lines without interfering with each other. The trigger manager is compliant with the PXI-9 PXI and PXI Express Trigger Management Specification. The KtMTrig driver can be used with any PXIe or AXIe chassis.

Keysight's IVI drivers simplify the creation and maintenance of instrument control applications in a variety of development environments. IVI drivers allow you to programmatically control your instrumentation while providing a greater degree of instrument interchangeability and code reuse. These drivers support compiling application programs for 32 or 64 bit platforms.

Volatile (dynamic) reservations will not persist through restarting (rebooting) the controller. Persistent reservations (also called static reservations) do persist through restarting (except in certain cases of conflicting reservations; see below). Connection Expert creates persistent reservations. The KtMTrig trigger utility (see above) creates volatile reservations.

You can interactively create or remove persistent trigger reservations and routes in Connection Expert's Chassis Triggers view to achieve the desired configuration. No changes are actually made to the system until you click Accept.

When you click Accept, your changes are communicated to the underlying Trigger Manager and thus to the chassis. At the same time, your changes are also saved as persistent reservations. This means that they will persist through a system restart (PC reboot or chassis power cycle). If some of your reservations/routes conflict with those made by another client, your conflicting reservations/routes will not be saved, but other non-conflicting reservations/routes will be saved; see Reservation Conflicts, below.

Example: Persistent Versus Volatile Reservations

Suppose your system includes the reservations and routes shown below. The Keysight_Persistent reservations were made in Connection Expert, and therefore they are persistent reservations. The My_test_client_1 reservations were made programmatically and therefore they are volatile.

You close Connection Expert and reboot your PC. Then you restart Connection Expert, and you see the following:

The persistent reservations are still present (have persisted) after the reboot. The volatile reservations are gone, and those trigger lines are available for new reservations.

The current state of a chassis' trigger lines (all current reservations and routes) is displayed in Connection Expert when you enter the Chassis Triggers view and select that chassis. At any time, you can reload the current state by clicking the Load Current State link at the bottom right of the window. However, if you have not saved your changes, they will be discarded when you load the current state. (If there are unsaved changes, you will be prompted to save or discard them.)

When you click OK to actually execute the reservation or route changes in the chassis, Connection Expert also loads the current state of routes and reservations created by other applications.

The time stamp just above the Load Current State link indicates when the current state was last loaded:

By reserving a trigger line, you declare to other clients that the reserved trigger bus segment is in use. The PXI-9 specification requires that a target trigger bus segment (the segment being routed to) must first be reserved by the client attempting to create a trigger route.

To reserve a trigger line:

1. Click the green reservation block that appears when you point to an unreserved trigger line:
   
   

2. When you click the green reservation block, it changes to a blue Keysight_Persistent reserved block.
   
   
3. Click Accept to execute the reservation in the chassis.

The line will be reserved by Keysight Connection Expert; you will see Connection Expert's client label, Keysight_Persistent, indicating this reservation.

You cannot reserve a trigger line that is already reserved by another application.

Reservation Conflicts

Connection Expert does not allow you to save routes or reservations that conflict with other applications. It may be difficult to work in the Chassis Triggers view while other applications are dynamically reserving and routing. If this is unavoidable, then make as few changes as possible in the Chassis Triggers view and then click Accept to save those changes before making more.

For best results, exit any running applications that may use trigger lines BEFORE reserving trigger lines or routing triggers in Connection Expert. You must force the applications to free their trigger reservations. They will normally do this as part of an orderly shutdown. After exiting the applications, you can check to be sure the reservations were freed by loading the current trigger state in Connection Expert's Chassis Triggers view. If an application does not correctly free its reservations (for example, if it terminates abnormally or is killed), you may need to restart the system to clear them.

When you click Accept to save your routing and reservation changes, it is possible that the changes you are trying to save will conflict with reservations and routes created by other applications. (This can only happen if other applications are running and modifying routes and reservations while you are editing them in Connection Expert.) In this case, the conflicting changes will not be saved in Connection Expert, and you will see an error indicator on the conflicting reservation:

If conflicts occur, the conflicting changes will not be saved, but any other non-conflicting reservations/routes will be saved.

There is no way within Connection Expert to unreserve a trigger line that has been reserved by another application. You must stop the other application or force it to release its reservation (see the Note above), then load the current state, before you can reserve the line in Connection Expert.

To unreserve a trigger line (that is, to cancel a reservation):

1. Click the Keysight_Persistent client label, or the reservation block beneath the client label on a reserved line.

2. Click Accept to clear the reservation in the chassis. The reservation will be cleared, and the line will now be free to be reserved by another client.

In Connection Expert, you can only unreserve a trigger line that is reserved by Connection Expert (Keysight_Persistent). If a line is reserved by another client, you cannot unreserve it in Connection Expert.

A trigger bus segment is the smallest unit that can be reserved for any trigger line. Reserving a bus segment reserves the trigger line for all the slots in that segment. Trigger routing controls whether and how the triggers move between bus segments of the same trigger line. You cannot route triggers between different trigger lines.

1. To create a trigger route, you must first reserve the trigger bus segment at the destination of that route. You should also reserve the segment at the source of the route, to indicate to other clients that it is in use so that they will not source triggers onto it. For example, to route from bus segment 1 to bus segment 2, you must first reserve bus segment 2, and it is recommended that you also reserve bus segment 1. This is illustrated below using trigger line 0:

2. When you reserve Bus 2, the routing arrows from left to right and right to left have a gray border, indicating that these routes are available. Click the arrow to create the route:

The arrow remains solid blue to indicate the route.

3. Click Accept to execute the route in the chassis.

If you wish to clear a route without creating the opposite route, click the blue arrow to toggle it off:

Click Accept to delete the route in the chassis.