National Instruments 781037-01 PXI Synchronization Module

The PXI Synchronization Module (National Instruments 781037-01) is part of the PXIe 6674T model line. It is intended to produce and route clocks and triggers amongst PXI Express chassis devices, as well as to other PXI and PXI Express chassis or third-party instrumentation. This module supports sophisticated low-voltage differential signaling (LVDS) trigger signals PXIe DStarA, PXIe DStarB, and PXIe DStarC, while also completely supporting the standard PXI trigger lines. It features a highly stable 10 MHz clock generated from an onboard precision oven-controlled crystal oscillator (OCXO) and a second clock derived from a direct digital synthesis (DDS) clock generation circuit.

The 781037-01 has a broad frequency range of operation; it can function at a minimum of 1 MHz and a maximum of 100 MHz for Clk10PLL, 200 MHz for FPGA, and an astounding 1 GHz for PXIe-DStarA. The module guarantees accurate timing with a maximum delay of 14.8 ns across the operational temperature range, and a typical ClkIn to PXI_Clk10_In delay of 6.75 ns at 25°C. Essential to the 781037-01's clock production capabilities is the OCXO, which has a nominal frequency of 10 MHz and can retain an accuracy of ±80 ppb after a year of calibration at temperatures ranging from 0°C to 55°C. With less than 10 ppb of peak-to-peak temperature stability, long-term stability is rated at ±50 ppb/year. 

All additional PXIe slots in a chassis that are directly connected to the System Timing Slot can be reached quickly by using PXIe-DStarB signals, which are LVDS signals. An analogous signal, PXIe-DStarC signals, which are likewise LVDS, come from additional PXI Express slots within a chassis and connect to the System Timing Slot. As a result, trigger or clock signals can be seamlessly shared between modules inside the chassis. By using PXIe-DStarC as a trigger source, the 781037-01 can use PXIe-DStarC to send signals received over that network to the PXIe-DStarA network for clock sharing.