Mini-WR-CB
Mini-WR-CB (Mini-WR Carrier Board) must provide power supply, mating connector and SFP module to serve the Mini-WR.
Power supply
Mini-WR need signle 3.3V supply voltage, current consumption depends on
the logic usage of the Spartan 6.
With current firmware to support dual SFP, 3.3V@1.3A (4W) is
required.
SFP module
The CB should connect the GTP pairs directly to the SFP module. The MDIO
and LOS signals of the SFP can be connected to Mini-WR if use Mezzostak
or Castellated edge connectors.
Two SFPs can be connected to support parallel mode or daisy chain mode
(similar to Cute-WR-DP )
WR recover clock and PPS
The 62.5/125MHz clock recovered by WRPC together with synchronized PPS are available for all connect options.
Data transmission
GMII signal group are available with Mezzostak or Castellated edge connect options. When using gold-finger connection, only partial of the GMII are used thus a customize protocol must be implemented between Mini-WR-G and the logic-process IC on the CB, bandwidth may be restricted.
Reference Design
Reference design of carrier board can be found in Mini-WR repository.
calibration
Since the traces link the Mini-WR with the SFPs sitting on the CB are part of the WR link path, the additional delay caused must be taken into account to guarantee the WR synchronization performance. Each customized CB must be calibrated to get the fixed delay value. Follow the White Rabbit calibration instruction. To reduce the link asymmetry cause by the fixed delay of Tx/Rx of the node, please keep the Tx/RX differential pairs equal-length, and through the similar routing topology to avid asymmetry variation caused by temp. change.