PCIe® has replaced PCI as the de facto expansion bus in laptops, desktops and servers worldwide. The embedded computing industry has responded by adding PCIe functionality into a number of modular electronic instrumentation platforms.
One example is PXI Express (PXIe). PXIe is typically found in electronic test equipment, automation systems, and modular laboratory instruments. PXIe leverages the faster speeds and increasing synchronization capabilities of PCIe® while offering backward compatibility with the large install base of legacy PXI and cPCI form factors.
What’s in a PXIe System?
PXIe systems generally consist of four main components. These include the following.
- A rugged chassis with integrated timing and synchronization
- Various plug-and-play I/O cards for configurable systems
- Control chassis via an external PC or an in-chassis embedded computer
- System level software for control and operation
In many applications, external control of the PXIe system provides benefits compared to in-chassis embedded computers. Communications between the external PC and the PXIe system can use many protocols, but PCIe® remains popular.
Linking the External PC to the PXIe System
Typical PCIe® cables offer support for various PCIe interfaces. While not suited for linking external PCs with PXIe systems, Samtec’s PCIEC Series of PCIe® Internal Cables Assemblies can handle x1, x4, x8 or x16 lanes.
External copper PCIe cables usually link external PCs to PXIe systems. In one example, Keysight Technologies specifies a 0.5m x8 Gen 3 PCIe® copper cable to link their M9049A PCIe HighPerformance Host Adaptor and their M9023A PXIe High Performance System Module.
Copper cables supporting high-speed PCIe® signals have finite lengths due to signal integrity limitations. In some applications requiring longer distances, switching to the optical domain is required. Fortunately, Samtec has the just the right solution.
PCIe® Active Optical Cable Assemblies
Samtec’s PCIe® Active Optical Cable Assemblies use lightweight 3 mm diameter cable to achieve Gen 3 PCIe® speeds up to 100m. The PCIEO series supports PCIe® auxiliary signaling (CPWRON, CPERST#, CPRSNT#, and CWAKE#) and features x4 and x8 lane options.
Keysight Technologies and Samtec have jointly tested the PCIEO series to offer an alternative link between the M9049A and the M9023A. From an operations/user standpoint, the copper to optical conversion is seamless while supporting much longer distances.
Additional details are available from Samtec’s Optical Application Engineers via firstname.lastname@example.org. For more information on running PCIe® over fiber, please download the following links: