Managed by the PXI System Alliance, with more than 65 members, PXI (PCI eXtension for Instrumentation) has been developed and introduced by National Instruments in 1997/98. PXI is based on the Compact PCI (cPCI) specification, defined in the mid 1990s. Both feature the same electrical characteristics as PCI, with a throughput of 132 Mbyte/sec (up to 256Mbyte/sec at 66MHz).
Using the same form factor as cPCI – the Eurocard format (IEC-297, IEEE1101.1, IEEE1101.10) – PXI adds system-level specs for synchronization and timing, cooling, environmental and EMI (Electromagnetic Interference) testing, software
framework and device driver (for automatic device recognition). The PXI interface uses 2mm pitch high-density, impedance-matched backplane
connectors (IEC-1076). Features specifically implemented in PXI to support test applications include:
• a System reference clock (10MHz TTL common reference clock for synchronization available on each slot with <1ns skew);
• 8 TTL trigger bus lines (for trigger, hand-shake, clock signals to be shared between modules);
• a Star Trigger bus (independent trigger line for each slot originating on Star Trigger slot, matched propagation delay <1ns); and
• a Local Bus (daisy-chained, 13 signals connecting each slot to its adjacent slot to the left and right, for analog signals up to 42V).
