Hi Everyone,
we have continued the bring-up of our system using the DP83822 in 100BASE-FX mode.
The communication is now reliable, but there is a problem with Link Detection.
To debug, we monitor BMSR at regular intervals.
Here is what happens when we connect to an external transceiver.
1 - Out of reset, with no fiber attached, the BMSR will show 0x7849 as expected (No Link).
2 -If we insert the RX fiber, Signal Detect is activated but nothing changes. Still 0x7849 (No Link).
**Signal Detect is driven at CMOS levels from a comparator.
3 - Then we connect the TX fiber. The register then shows 0x784D (Linked).
4A - If I disconnect the TX fiber, the register becomes 0x7849 again.
4B- If instead I disconnect the RX fiber, Signal Detect is deactivated but nothing happens and I still read 0x784D.
It looks as though the DP83822 only uses Far End Fault from the remote device to determine if there is a link or not. Is this the case?
Is there something I can do to make the DP83822 see the Signal detect input correctly, so it can also send Far End Fault signals?
Here is how we have strapped the PHY: 0x467 reads 0x4503 and 0x468 reads 0x0001 (see the description of the straps in the attached file)
- I don't know how to configure the EEE_EN strap. Should it be enabled or not in 100BASE-FX mode?
- Also, the LED_1 configuration strap has been set to Tri-State. Is this OK if I use it as Signal Detect?Straps.docx
Thanks!
