Hi,
I'm trying to use a National DP83849IF DUAL PHY in 100FX mode for a media converter application, but other than IDLE, FEFI and BIST signals I cannot get any data off the port in FX mode.
For testing, one port of the PHY is wired to magnetics for 100TX operation, the other port only has some resistors so that I can see what's going on with a a scope.
When configured for 100TX-100TX "extender" mode, everything works as expected. Data received on the wired port causes the activity LED to blink there and blinking can be observed on the other one as well. Same holds true for data sent to both ports at once via MII.
But if I configured the port connected to the scope for 100FX or even if I just manually disabled the scrambler for that port in TX mode (so that output on the scope would be more "human-readable"), that port will go and output only IDLE (62,5 MHz, almost square wave) and Activity LED is lit continuously.
I tried various settings but still haven't had any success. That thing won't transmit data in 100FX mode. Is there anyone who successfully uses this PHY for 100FX?
- No difference whether MII or RMII
- "Signal Detect" is forced in register
- If Signal Detect wasn't forced and FEFI is enabled, I can see FEFI zeros
- Link and Activity LED are constantly lit whereas with the same LED configuration in TX mode only Link is lit and Activity only blinks when data is transmitted
The only things that I can think of which isn't right out of the data sheet is that the PHY always starts strapped for 100TX with auto-negotiation; 100FX mode is configured via register reprogramming afterwards. And Signal Detect input isn't actually connected (but I tried hardwiring a logic high there with a voltage divider once and it didn't make a difference, it wasn't detected at all...)
Thanks for all suggestions and comments in advance!
Kolja