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Altera_Forum
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17 years ago

ALT2GXB loopback problem

Hi, I'm using an Arria EP1AGX60CF484C6 with an ALT2GXB core configured in XAUI mode (4 lanes). I'm trying to do a loopback to test it out. The loopback is in the core, so what I've done is con...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

Hi,

Just an update and some new issues.

I put a state machine to carry out the reset sequence and I put in the calibration clock in too. But it still doesn't work.

In simulation, I discovered that I had to feed the Rx pins K28.5-, K28.5+, K28.3- and K28.3+ in order to get a '07' (Idle) state out of the rx_dataout port. I could then see this idle state data loop it's way around the Tx side and see some activity on the Tx pins that seemed to make some sense. This was all in simulation. Does this mean that after the reset sequence, the GXB block has to be put into idle state before it will accept data?

However, we've also discovered a problem with the Tx output voltage. It seems to be around -40mv to +40mv. We'eve done all the usual checks on the board with supplies etc. but haven't found a problem. We tried with and without calibration resistors and it does make a difference to the output.

Any idea's will be most welcome.

Regards

MT