Hello, I am trying to write a simple template frame transmitter using MII in verilog. The ethernet frame format I am using looks like preamble (7B) > frame delimeter (1B) > Dest. MAC (6B of 1's to broadcast) > Source MAC ( 00:11:22:33:44:55) > LENGTH (4B, typing 100 for 100 octetcs of data) > DATA (100 octets of 0's) > FCS (4B, calculated using http://www.zorc.breitbandkatze.de/crc.html) with data (from dest MAC to the end of actual data) i've just provided. I am aware of the fact of reverse order of bits needed by the ethenret frame. To capure any data from PHY i am using Wireshark, but it shows only some frames from the PC (used, for example, to establish connection or trying to communicate, i guess). Is the timing of TXEN correct? Or is it something wrong with the implementation? I would appreciate any help in making the code sending that frame. (The files attached presents the code itself and the start and end of frame to be transmitted (to show the TXEN timing)
What is your target platform for the Verilog code? From what I read it sounds like you are trying to run Verilog code on your PC to send something through your PC network card.
The transmitter code is a part of a bigger project. It runs on a Lattice LFXP2 fpga. The FPGA is connected to MTXC (the clk of the module) MTXEN, MTXER and MTXD3-0 of PHY device (KSZ8863). PC network card is connected to the PHY device. I can see that the link is established to 100Mb/s (what is correct since the external crystal provides 25MHz). Wireshark does not show any packet from the PHY.
Are you syncing the tx signals to the external clock? Are you sure your CRC is correct? Are you sure that your PHY really sends your packet? Most PHYs have a loopback that can be enabled for debug. You could test if your PHY responds by enabling a loopback to PC side (and send sth. to the PHY, i.e. using Ostinato) and you can test if your PHY would really send your packet with the loopback to MAC side.
1. they are synced to the MTXC pin that is PHY transmit clok pin. 2. it can be as correct as the internet caclulator done it (but i have used MIIM to make a change in phy's control register to switch all packages, including bad ones). 3. no, i am not, since neither wireshark nor etherdetect shows anything. The is only a TX side used for now, so a loopback may not come in handy.
I have written also a MII interface in VHDL see Beitrag "Ethernet GMII" The starting code has a mistake in the preamble.
Dose wrote: > I have written also a MII interface in VHDL > > see > Beitrag "Ethernet GMII" > > The starting code has a mistake in the preamble. That would Wireshark not prevent to see something. But a fully functionally Wireshark requires a network card which can be set to promiscous mode and that also will forward packets with incorrect FCS. It is also advisable to use a driekt (crossover) connection, as switches also drop errornous packets.
Dose wrote: > The starting code has a mistake in the preamble. now it is 14x 0x5 then 0xD and 0x5 (as in https://en.wikipedia.org/wiki/Ethernet_frame) As far as I understand Your code, it should be 13x 0x5, 0xD and than start of mac addressing?
Szymon P. wrote: > now it is 14x 0x5 then 0xD and 0x5 (as in > https://en.wikipedia.org/wiki/Ethernet_frame) > > As far as I understand Your code, it should be 13x 0x5, 0xD and than > start of mac addressing? This is because of GMII is sending a byte at once and MII is sending two nibbles with least significant nibble first. So > now it is 14x 0x5 then 0xD and 0x5 (as in should be okay. Regarding the FCS, you could just send the frame with the 100 zero bytes from your PC (I already mentioned Ostinato which has a GUI and runs on Win/Linux but there are other command line tools also) and monitor it with wireshark, then compare the FCS that is automatically created with your FCS. Also you can configure your PHY in loopback mode to PC side to know if your network card is in promiscuous mode. For both you do not need to implement an RX in your FPGA.
Szymon P. wrote: > Dose wrote: > >> The starting code has a mistake in the preamble. > > now it is 14x 0x5 then 0xD and 0x5 (as in > https://en.wikipedia.org/wiki/Ethernet_frame) > Which is wrong. The IEEE 802.3 standards are part of the IEEE get program and available free of charge: http://standards.ieee.org/about/get/802/802.3.html MII is described in section 2, chapter 22. Table 22-3 shows exactly how to send the preamble.
> Table 22-3 shows exactly how to send the preamble.
You are right, thanks.
About checking FCS on wireshark or Ostinato, they just do not show any
:/
Packets (raw ethernet frames, still without fcs shown) from Ostinato are
captured as Malformed Packets with ARP protocol.
Szymon P. wrote: > Packets (raw ethernet frames, still without fcs shown) from Ostinato are > captured as Malformed Packets with ARP protocol. And are they returned when you enable PHY external loopback? Maybe you should also set a valid ether type, as otherwise this may be interpreted as length and may be discarded by your network card.
hi, just google for Colasoft Packet Builder and download it. You can fill in your own Packet (bytewise) and it will calculate the CRC32 for you. I am using this programm to check the CRC32 values from my Ethernet packets, it works.
In Wireshark have you set the promiscuous mode under capture options?
Ok, then, what about bit order. I assume that if my TX is (phytx3,phytx2,phytx1,phytx0) and i want to transmit 0x0806 I should do it like: TX<=4'b1000; TX<=4'b0000; TX<=4'b0110; TX<=4'b0000; But what about FCS? The wiki states: "the least-significant bit is transmitted first, except for the frame check sequence (FCS)." For example, let the first byte of FCS be 0x14; Should I do it the same way? (transmit 4, then 1), transmit it "as is" (1, then 4)...or reverse it from 0b00010100 to 0b00101000 and transmit it like 2 then 8, or 8 then 2?
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