On the Rev 1.0 version of the KC705 board, the FPGA SFP/SFP+ transmitter signals MGTXTXP2 and MGTXTXN2 are swapped.The SFP/SFP+ receiver signals MGTXRXP2 and MGTXRXN2 are also swapped.
SFP/SFP+ Loopback tests or connections to another Rev 1.0 KC705 board work successfully with or without changing the TX and RX polarity control.
When designing with the KC705 SFP/SFP+ transmitter (MGTXTXP2, MGTXTXN2) interface, the FPGA's GTX TX polarity control should be used to change polarity and compensate for the transmitter's MGTXTXP2, MGTXTXN2 pin swap. No other changes are required for normal operation.
Definition of TX polarity control from the 7 Series Transceiver User Guide is repeated below:
TX Polarity Control
If TXP and TXN differential traces are accidentally swapped on the PCB, the differential data transmitted by the GTXtransceiver TX is reversed.One solution is to invert theparallel data before serialization and transmission to offsetthe reversed polarity on the differential pair.The TX polarity control can be accessed through the TXPOLARITY input from the fabric user interface. It is driven High to invert the polarity of outgoing data.
Likewise, when receiving a signal on the KC705 SFP/SFP+ receiver (MGTXRXP2, MGTXRXN2) the FPGA's GTX RX polarity control should be used to change polarity and compensate for the receiver's MGTXRXP2, MGTXRXN2 pin swap. No other changes are required for normal operation.
Definition of RX polarity control from the 7 Series Transceiver User Guide is repeated below:
RX Polarity Control
If RXP and RXN differential traces are accidentally swapped on the PCB, the differential data received by the GTXtransceiver RX are reversed. The GTX transceiver RX allows inversion to be done on parallel bytes in the PCS afterthe SIPO to offset reversed polarityon differential pair. Polarity control function uses the RXPOLARITY input, whichis drivenHigh from the fabric user interface to invert the polarity.
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