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AR# 31791

Virtex-5 RocketIO GTP - RXP/RXN recommendations in an unused tile

Description

Keywords: unused, GTP, MGTRXP, MGTRXN, RXP, RXN, ground, floating

Previous versions of the Virtex-5 FPGA RocketIO GTP Transceiver User Guide indicated that for an unused GTP, the MGTRXP and MGTRXN pins could be either left floating or tied to ground on the board. The current documentation indicates that they should be tied to ground. Which is correct?

Solution

In an unused GTP, the termination resistors will connect each of the receive pins to MGTAVTTRX, which for an unused tile will be tied to ground. With this being the case, leaving the MGTRXP and MGTRXN pins floating or tying them explicitly to ground will have the same result. Boards that have left MGTRXN and MGTRXP floating as recommended by earlier user guides are NOT at risk for failures or decreased margins as a result.
AR# 31791
Date Created 10/13/2008
Last Updated 10/13/2008
Status Active
Type General Article