Using PEX 8648 SMA Based (SI) Card White Paper – Version 1.3
© 2010 by PLX Technology, Inc. All Rights Reserved
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8 Using Two SI Cards for Link Testing
Another means of testing employs the use of two SI cards. This approach can be used in three
connectivity scenarios:
1) One root complex (PC) to control the PCIe link and one base card (i.e. PCIe compliance load
board) to provide power to the downstream card. The default clocking for this configuration is
asynchronous (hence PC clock must not set SSC active) or an out of band reference clock is fed
into the downstream card. The downstream card is configured to have the SMA port as the
Upstream. (
Note: it is necessary for both cards to see at least one reset in order to initiate link-up
negotiation. If needed, manually depress card reset switch)
2) Two root complex systems – each SI card is placed in a PC and the SMA ports connected.
Typically, in this configuration, NT is employed to allow Host-to-Host connectivity. Standard
clocking is again asynchronous. (
Note: it is necessary for both cards to see at least one reset in
order to initiate link-up negotiation. If needed, manually depress card reset switch)
3) One root complex, stacked connectivity – as shown below. In this configuration, coherent
clocking is maintained between cards. Consequently, the PC can have SSC enabled. If alternate
reference clock injection is desired, it is done so by changing the RefClk input configuration on
the bottom SI Card unit. Examples for this configuration are discussed.
Figure 5. Single PC connectivity
