Using PEX 8648 SMA Based (SI) Card White Paper – Version 1.3
© 2010 by PLX Technology, Inc. All Rights Reserved
3
3 Configuration
The PEX 8648 is a three station Gen 2 switch device with 48 maximum SerDes lanes. The SI RDK uses
only stations 0 and 1. The first station – Station 0 – contains both the default upstream port (Port 0 –
feeding a standard PCIe connector) and also four SMA output lanes on an additional port (Port 3 –
Downstream) – used for direct data observation and reception without the degradation of the PCIe
connector. The transmitter and receiver pairs of each lane of the port are clearly marked with lane and
polarity (however, it is not necessary to track lane polarity as this is automatically resolved by the PCIe
specification).
The PCIe connector at the top of the PCB is an alternate PCIe connection, located off of station1 of the
switch (Port 6). It is not typically needed for SI use, but if desired a second card (including another SI
RDK) can be installed and operated off the same base reference.
Below are block diagrams of the port connections (
Figure 1
) and clocking
(Figure 2
).
Figure 2. PEX 8648 SMA Card Port Configuration
