Electronic – DP83848 (Ethernet PHY) 1-bit serial receive data in 10Base-T

ethernetmacphy

Having trouble getting a Texas Instruments DP83848J working in 10BASE-T mode.

The link partner and local status register agree that the link is in 10Mbps full-duplex mode. However, instead of receiving 4-bit 2.5Msps data on RXD[3..0] as required by the MII spec, a logic analyzer shows 1-bit 10Msps data. The only Ethernet standard I can find that describes that type of data is GPSI, which is not part of the DP83848J feature set.

Any idea how to configure the DP83848J to output data compliant with the 10 Mb/s MII Timing spec?

Best Answer

You are probably in RMII (reduce MII mode). Check this registers:

7.2.5 RMII and Bypass Register (RBR)

And this pin:

MII_MODE (RX_DV) 32 MII MODE SELECT

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