Hello TI Team,
we have 2 Evalboards (self-made) with TLK2501 on each board. The data transmission is bi-directional and each board has independent clock source (i.e. 125MHz; accuracy according to datasheet 100ppm).
The settings are identical for both boards:
TESTEN: low
PRBSEN: low
LCKREFN: high
ENABLE: high
TX_ER: low
LOOPEN: low
TX_EN: high
The high speed serial side (TXP, TXN, RXP, RXN) is configured as AC-coupling with termination as stated in the datasheet (with RREF=200 Ohm).
Case 1:
We connected the boards with SFPs (CML compatible, internal AC-coupled). TD0-TD15 on both boards are permanent high.
In this case, RX_DV and RX_ER on both boards are high and we get random state on RD0-RD15 on both boards (some high, some low).
According to the datasheet, the high speed receiver side is also compatible with CML level. What could be the reason? How can we connect/interface the TLK2501 to SFP?
Case 2:
We replaced the SFP connection with 50 Ohm SMA cable. TD0-TD15 on both boards are permanent high.
In 70-80% the case, we got RX_DV: high and RX_ER: low on both boards. RD0-RD15 are permanent high on both boards. Everything's fine.
The rest is that we got on one board RX_DV and EX_ER: high and on the other board RD_DV and RX_ER: low. RD0-RD15 on both boards are with random level.
The problem is fixed if we power-reset the boards or just disabled and then enabled the boards.
What could be the reason that the boards didn’t sync properly directly after power up?
Additional information: internal loopback function properly on each board (LOOPEN: high), external loopback with SMA cable function properly on each board for itself (LOOPEN: low), PRBS test between two boards function properly (PRBSEN: high).
I'm looking forward to hearing from you soon.
Regards,
Theresia
