NI-TClk
Homogeneous and Heterogeneous Triggers
NI-TClk provides a simplified interface for synchronizing systems with homogeneous triggers in a single PXI chassis or PC. NI-TClk also provides a flexible interface for other supported systems.
Triggers Supported by NI-TClk
The following table summarizes the triggers supported by NI-TClk.
| Trigger | Acquisition | Generation |
|---|---|---|
| Start Trigger | Yes |
Yes |
| Reference Trigger | Yes |
N/A |
| Script Trigger 0 – 3 |
N/A |
Yes |
| Pause Trigger | No |
Yes |
Individual instruments may support some or all of the triggers listed in the previous table. Instruments may also support triggers other than the ones listed in the previous table. These other triggers, as well as pause triggers for acquisition sessions, are not supported by NI-TClk and are not relevant to the definition of homogeneous triggers. For information about which triggers your device supports, refer to the device user documentation.
Homogeneous Triggers
For purposes of TClk synchronization, synchronized sessions are defined to have homogeneous triggers if the triggers are synchronized. To get synchronous triggers, set only the master session (the first session by default) to use a software trigger. If not explicitly set, slave sessions use the same trigger source as the master session.
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Note When a supported trigger is not configured, it is referred to as None. Refer to Comparison of Terminology between NI-TClk, NI-HSDIO, NI-SCOPE, and NI-FGEN for more information about trigger terminology. |
Also, for each of the other triggers supported by NI-TClk, one of the following statements must be true:
- Trigger is not supported by any of the sessions.
- Trigger is configured as None by all sessions that support it.
- One of the sessions, called the trigger master session, is configured to receive the trigger from the external world (in case of external triggers) or to generate that trigger (in case of None or software triggers), and the corresponding trigger on all other sessions is configured so that it comes from the trigger on the trigger master session.
If there is a trigger master session, non-master sessions must use the triggers that they receive from the trigger master session for the same purpose as the trigger master session. For example, the reference trigger from the reference trigger master session must be used as the reference trigger for the non-master sessions.
The type of trigger (for example digital edge, analog hysteresis, or software) for the trigger master session is not relevant for this definition. The type of trigger for non-master sessions must be digital edge or digital level because the trigger coming from the trigger master is a digital signal.
With TClk synchronization, all sessions react to a synchronized trigger at the same time.
Heterogeneous Triggers
Sessions are defined to have heterogeneous triggers if they do not have homogeneous triggers. If any of the conditions from the definition of homogeneous triggers are not true, the sessions are considered to have heterogeneous triggers.
Examples
Example 1: Homogeneous Triggers
Sessions A and B have triggers as indicated in the following table.
| Trigger | Session A (Generation) |
Session B (Generation) |
|---|---|---|
| Start Trigger | Configured as software trigger | Configured to use start trigger from session A |
| Reference Trigger | Not supported | Not supported |
| Script Trigger 0 – 3 |
Not supported | Not supported |
| Pause Trigger | Not supported | Not supported |
Sessions A and B have homogeneous triggers.
Example 2: Homogeneous Triggers
Sessions A, B, C, and D have triggers as indicated in the following table.
| Trigger | Session A (Acquisition) |
Session B (Acquisition) |
Session C (Generation) |
Session D (Generation) |
|---|---|---|---|---|
| Start Trigger | Configured as None | Configured to use start trigger from session A | Configured to use start trigger from session A | Configured to use start trigger from session A |
| Reference Trigger | Configured to use reference trigger from session B | Configured as analog edge trigger | Not supported | Not supported |
| Script Trigger 0 – 3 |
Not supported | Not supported | Configured as None | Configured as None |
| Pause Trigger | Not supported | Not supported | Configured as None | Configured as None |
Sessions A, B, C, and D have homogeneous triggers. Notice that session A is the start trigger master session, and session B is the reference trigger master session.
Example 3: Heterogeneous Triggers
Sessions A, B, and C have triggers as indicated in the following table.
| Trigger | Session A (Generation) |
Session B (Generation) |
Session C (Generation) |
|---|---|---|---|
| Start Trigger | Configured as software trigger | Configured to use start trigger from session A | Configured to use start trigger from session A |
| Reference Trigger | Not supported | Not supported | Not supported |
| Script Trigger 0 | Configured as digital edge | Configured as None | Configured as None |
| Script Trigger 1 – 3 |
Configured as None | Configured as None | Configured as None |
| Pause Trigger | Configured as None | Configured as digital level | Configured to use pause trigger from session B |
Sessions A, B, and C have heterogeneous triggers because neither the script trigger nor the pause trigger comply with any of the three required conditions, of which at least one condition must be met, for the reference, script, and pause triggers.
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