ADLINK aTCA-N700 - Manual (Page 31)

aTCA-RN710 User's Guide
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6 Data Path: SFP+ and Retimer
6.1 Overview
The retimer used on the board is essential to improve the 10Gbps SFI signal quality. According to
SFF 8431 specification, the SFI signal may not reach from a front blade to an RTM SFP+ port or vice
versa, at viable quality after traversing a Zone 3 connector and several vias on the lossy PCB. The
retimer along with equalization features compensates such losses and reflections. The retimer used
on the board is quad retimer GN2405A from Gennum. Shown in Figure 6-1 are the six retimers and
twelve SFP+ ports which are connected to the corresponding switch ports on the front blade via the
Zone 3 connector(s). A single GN2405A covers dual SFI+ RX/TX paths in an asymmetric way. It is
asymmetric in a sense that the path characteristic from the front blade (via Zone 3 connector) to the
retimer input and the one from the SFP+ RX to the retimer input are significantly different. So each
one of the path should be configured differently, meaning different adjustment may be applied for the
different path characteristics for all the devices.
Figure 6-1 SFP+ and Data Path