Software really is the test instrument. Lecroy's BitTracer, which runs on the PETracer Gen2 Summit PCI Express Protocol Analyzer, provides a physical-layer view of PCI Express traffic that's similar to what a logic analyzer might display. But it also provides this capability on a protocol analyzer. Designers can view the bit stream traffic before it's decoded into high-level packets to better understand what signal integrity issues may be causing data corruption.
Most PCI Express designs typically require a logic analyzer and a protocol analyzer to work together to solve tough troubleshooting and debug issues. This often involves attaching and disconnecting the logic analyzer multiple times, which can be a real pain. The BitTracer software eliminates this problem with one piece of equipment that can display the logic analyzer states listings yet still show the packet information.
The BitTracer software displays all bits in the bit stream for each individual PCI Express lane (see the figure). These bits are shown just as they appear in the multi-striped bit stream. A separate window in the display shows the high-level packet generated from the presented bits. Both window displays correlate as users examine the bit stream clearly showing the nature of any corrupted packets. The BitTracer software also includes traffic summary and search features.