XI Express or PXIe is a subset of the PXI standard that replaces PXI’s parallel data bus with a high speed serial interface. PXIe provides the most advantages for modular instruments like digitizers or arbitrary waveform generators which often need to transfer large amounts of data. For example, state-of-the-art PXIe products from Spectrum incorporate a fast interface that can stream at rates of up to 1.7 GB/s.
The following PXIe features are supported by the Spectrum cards of the M4x series:
- PXIe 100 MHz Differential Reference Clock: A PXIe chassis also offers a 100 MHz high frequency differential clock called PXIe_CLK100 which is supplied to the system timing and hybrid peripheral slots. The skew for this clock is less than 100ps. If used, the PXIe_CLK100 lines must be terminated on the peripheral. There is also a differential synchronization signal, PXIe_SYNC100. This signal is synchronous to PXIe_CLK100 and asserts one out of every 10 clocks to indicate the phase relationship of the 10 MHz and 100 MHz reference clocks.
- PXI 10 MHz Reference Clock: by software command the supplied 10 MHz PXI reference clock can be used as base for clock generation.
- PXI Star-Trigger: by software command the card can accept the star trigger line as trigger signal. A separate star trigger card is needed.
- PXI Trigger Bus: each Spectrum PXIe card can use PXI trigger line 0 to 7 as a trigger input or can output its internal trigger signal to one of the lines.
- Slot-to-slot local Bus: not supported.
The Spectrum PXIe cards run in dedicated PXIe slots as well as PXI/PXIe hybrid slots. The M4x series of cards occupies two slots width.