# MII SFD Detection with FPGA Logic

• posted

Hello,=20 I have to detect the Start of a Ethernet Frame. So I want to make use of a = FPGA. The FPGA will be connected to the MII pins of the PHY (TXD 0-3 and RX= D 0-3, the Clocks, TX_EN and RX_DV). What I know from the IEEE802.3 Datashe= ets is that the preamble will be send as 14 Nibbles and after that 2 Nibble= s the SFD. In transmitting case it will be like that:=20 TxD0 X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Data=20 TxD1 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Data=20 TxD2 X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Data=20 TxD3 X 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 Data=20 TxEn 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1..=20

So I thought that I can trigger the rising edge from TxD3 in the 16. Cylce = or from Tx_En. But if I only check one wire there could be errors right? Ho= w do I check for more than one Cylce? Do I need a State machine? Is this th= e correct path?=20

I found the example of SFD detection from OpenCores.org of the EtherMac pro= ject, but i dont have any verilog or vhdl knowledge. =20 Thatswhy i wanted to use the Xilinx ISE Schematic tool and some fast logic.

So can you help me by giving me some advice how to make use of some fast lo= gic.=20 Do i need some FIFOs oder Latches?=20

Thank you very much and greetings

• posted

(snip)

If you can understand digital logic, how it is wired together, for example in thinking about how to wire together 7400 series ICs, you will have an easy time learning either Verilog or VHDL.

Think in terms of wires and gates, write in either HDL.

Once you know one of Verilog and VHDL, you will almost be able to read the other.

Then learn just a little about the other, and you can easily read it, too.

-- glen

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