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Visitor fernands
Registered: ‎01-22-2014

GTP Receiver Detection

Hello everyone,


I am trying to implement a module that connects to a GTP Dual and, as an output, tells if a a receiver is present or not.


The GTP is used together with a custom protocol and connected to an SFP entry. I am using a Virtex5 xc5vlx50t . The GTP is generated with Bypass Tx/Rx Buffer, clock resources are shared (one MGT per TX/RX clock) and Enable PCI Express mode is on. The protocol works with no problem. 


According to the documentation for RocketIO, TXELECIDLE is fixed to '1' and the module for checking the cable does the following (all of this at TXCLK2 clock domain) :


1) When the intention of checking if a cable is present, TX/RXPOWERDOWN are asserted "10"

2) A RXRESET is preform according to pg. 95 Note 3

3) Wait for RESETDONE to be '1'

4) Assert TXDETECTRX '1'

5) Wait for PHYSTATUS to be '1', assert TXDETECTRX '0' and put TX/RXPOWERDOWN are asserted "00" 

6) RXRESET again

7) Wait for RESETDONE to be '1'


In the RXCLK2 domain, I just wait for PHYSTATUS to be '1' and  and then update the output of cable present according to the value of  RXSTATUS (if '011' then '1' else '0').


xI tested the module and it seems that once I put a SFP connector, without any fiber cables, the RXSTATUS changes to 3. But it is not consisting. Is there anything that I overlooked? Thank you. 


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1 Reply
Registered: ‎02-16-2010

Re: GTP Receiver Detection

Regarding your steps, I find RXRESET is not required at step#2. It is required only after step 5 in your flow.

It looks like SFP connector is serving as a far end termination as shown in figure 6-15. If possible, can you check with a SMA interface?
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