You can synchronize digital pattern instruments to varying degrees.

  • You can operate instruments independently with triggers and events passed between instruments to coordinate operations.
  • You can use the NI-TClk API to phase align the internal clocks of all the instruments. Use the API to route triggers deterministically so that all the instruments respond to and receive triggers at the same time.
  • In the Digital Pattern Editor, you can use the same instrument group name in the pin map for multiple instruments. This automatically aligns the internal clocks of the instruments in the group and routes triggers deterministically.
Note You can group digital pattern instruments of only the same model and channel count, and the instruments must be in the same chassis. For example, you can group two PXIe-6570s of matching channel count that are within the same chassis but not a PXIe-6570 and in the same chassis.
Note You can open a synchronized multi-instrument session by passing multiple instruments into the Initialize with Options API. Refer to the Digital Pattern User Manual for more information.

After aligning the internal clocks and routing triggers, you can use a PXIe-6674T in the chassis. The PXIe-6674T combines pattern comparison results across digital pattern instruments. This module also controls subsequent pattern execution based on those results. Refer to the PXIe-6674T User Manual for information about installing PXIe-6674T in the timing and the synchronization slot of the chassis.

Note You cannot disable the synchronization without recreating the instrument session.

Internal Clock Phase Alignment

The MasterClk internal clock locks to the PXIe_CLK100 signal for digital pattern instruments. To synchronize other instruments with a digital pattern instrument, you must lock their internal clocks to PXIe_CLK100.

Note Internal clocks are also known as Sample clocks.

System Timing Alignment

The NI-TClk API included with an installation of the NI-Digital Pattern Driver aligns the timing reference on synchronized instruments. For instruments used inside a Semiconductor Test System (STS), the timing calibration procedure aligns the timing across all digital instrument channels. On systems without STS timing calibration, enable the Timing Absolute Delay property to adjust the timing reference on synchronized instruments for better timing alignment, measured in seconds.

Trigger Routing

NI-TClk uses the PXI trigger bus to deterministically route triggers among multiple instruments. This trigger route ensures that all instruments in the system execute at the same time. Deterministic trigger routing ensures that all instruments in the system start at the same time. Refer to multi-device NI-TClk examples for more information about the NI-TClk API. Refer to the NI-TClk Synchronization Help for more information on using NI-TClk to synchronize instruments.

Using Matched and Failed Opcode Parameters with Synchronized Digital Pattern Instruments

During a pattern burst, the digital pattern instrument pattern sequencer controls the matched and the failed parameters of the jump_if and exit_loop_if opcodes. You must configure the system when you burst patterns that use the matched and the failed parameters across multiple synchronized digital pattern instruments. To configure the system to combine comparison results across the digital pattern instruments, complete the following steps.

  • Use the NI-Sync 16.1 or later to initialize the PXIe-6674T timing and synchronization instrument.
  • Use the niTClk Synchronize API to align the internal clocks and route the triggers of the digital pattern instruments.
  • Use the niDigital Enable Match Fail Combination API to enable each synchronized instrument to process the combined comparison results.

Configuring a system to combine matched and failed results causes a TRUE result for any failed condition on any site enabled for bursting across multiple synchronized digital pattern instruments. This TRUE result affects the pattern execution flow through opcodes that use the failed condition as a parameter. Calling the niDigital Get Site Pass Fail API on all digital pattern instruments returns failed results only for the sites on the instruments responsible for the failure.

When you configure a system to combine matched and failed results, the combined system result for the matched condition is TRUE only when all sites enabled for bursting across multiple synchronized digital pattern instruments satisfy the matched condition, including pins in the specified match condition.

Table 7. Common Use Cases and Behavior
Use Case Behavior
  • Single PXI Express chassis
  • Single digital pattern instrument
  • Multiple sites
  • Without PXIe-6674T
 If you require per-site matched and failed capability, create a site loop in the test program. The site loop enables you to burst the pattern for each site sequentially.
  • Single PXI Express chassis
  • Multiple digital pattern instruments
  • Multiple sites
  • Without PXIe-6674T
  • The pattern sequencer in each digital pattern instrument might not execute the same vector at the same time.
  • If you assign a single site per digital pattern instrument, each site can process the matched and failed parameters independently. Each site can also independently execute conditional opcodes in parallel.
  • If you assign multiple sites per digital pattern instrument and require per-site matched and failed capability, create a site loop in the test program. A site loop allows you to burst the pattern for each site sequentially.
  • Single PXI Express chassis
  • Multiple digital pattern instruments
  • Multiple sites
  • With PXIe-6674T
  • All digital pattern instruments within a single chassis become a single digital subsystem and execute the same vector at the same time, including flow control operations. Instruments and sites assigned to this digital subsystem don't branch independently.
  • If you require per-site matched and failed capability, create a site loop in the test program. The site loop allows you to burst the pattern for each site sequentially.
Multiple PXI Express chassis Each chassis operates independently.