02-17-2014 05:23 PM
The TX and RX USRCLKs can be shared between transceivers within the same QUAD under certain circumstances.
My question however is, are the 4 different TX and RX USRCLK outputs all exactly the same, or are there phase differences between them?
Each lane seems to have a different Tx and Rx fabric clock divider, but all sourced from the same PLL, so not sure about this one actually. It doesn't really mention anything about this in documentation.
02-17-2014 07:26 PM
I think you should expect minor phase differences due to the path difference travelled by the CLOCK input to the different quad's and also if there are any setting difference between the quad's. However i guess you are looking for multlane appliications.
However if you are looking for Multilane applications check below
TX Multilane can be found from Pg 90 of UG371 - LINK
Configuring the Transmitter for Multi-lane Applications
The GTHX4LANE port in GTH transceivers is used for multi-lane applications that require
minimum skew across channels. To configure four GTH lanes within a Quad into a single
x4 link, GTHX4LANE must be tied High. When configured in a single x4 link, a change in
the control settings on the master lane also causes the same effect on the slaves. An
exception to this is the POWERDOWN port. In this x4 link configuration, the buffers across
the four transmit data converter are synchronized for minimizing skew.
RX Multilane can be found from Pg 147 of UG371
To configure four GTH lanes within a Quad into a single x4 link, the GTHX4LANE port
must be tied High. When configured in a single x4 link, a change in the control settings on
the master lane also causes the same effect on the slaves, except with the POWERDOWN
ports. The POWERDOWN ports of all GTH lanes within a Quad in a x4 link should be
driven by the same source.
02-17-2014 07:38 PM
02-18-2014 08:03 PM
Is your query resolved? Lets us know if you need any further help.