Hello, I have a design that's using a DM8147 processor and connecting a DP83848K PHY for 10/100M Ethernet. We're trying to bring up the board and I'm stuck debugging this and could use some ideas on where to look. Here are the vitals:
- Using WEC7 and attempting to issue a DHCP request from eBoot to see if we can boot over EMAC0.
- Using RMII to EMAC0 on the DM8147 and having the DM8147 supply the 50 MHz refclk to the PHY.
- PFBIN1 and 2 are at +1.8V.
- RBIAS pin measures +1.2V.
- Supplies and termination bias are at +3.3V.
- Clock to the PHY looks good at 50 MHz with no ringing or reflections using an active probe.
- REFCLK and the TX data line to the PHY use 22 ohm series resistors and are matched length in the layout.
- The PHY undergoes a reset pulse and the strapping resistors are in place to put it into RMII mode (2.2K pull-up on pin 32).
- I leave the PHY address bits alone to default to "00001".
- One thing I did not do was pull down the other two TXD inputs to the PHY by design but I did make a mod to do this.
- When the board comes up and takes the PHY out of reset, I can see the link light on both the router and my board Ethernet jack light up.
- eBoot is able to communicate with the PHY over the MDIO bus (488 kHz for some reason) and indicate that the PHY is in 100M, full-duplex mode.
- When we change the boot mode to use EMAC0, we get nothing but timeouts when DHCP requests are sent out.
- I've probed the TX_EN and TXD[0] and TXD[1] traces and they do indeed toggle when the requests are sent out.
- I have my PC also plugged into the same LAN side as my board to monitor Ethernet traffic using Wireshark looking specifically for DHCP packets. I can see my PC issue a request and it gets a response from the router issuing it an IP address. However, absolutely nothing from my board when DHCP requests are sent (being monitored in eBoot console).
I've attempted to provide the schematic below of the PHY and jack. Some questions I have:
- I'm not sure if this is a hardware or software issue at this point. The software team has indicated they have properly configured the EMAC for RMII and it appears data is coming out the TX data pins as well as the TX_EN on each DHCP request attempt.
- The magjack I'm using does NOT have the Bob Smith termination - is this required?
- What else can I look at?
Thanks in advance!