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beandigital
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Registered: ‎04-27-2010

Xilinx TEMAC TUSER signal

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I am trying to simulate the Xilinx TEMAC. I am using the example design but I have modified the testbench to send an ARP packet.I have copied this from a Wireshark capture. The data that comes out of the MAC rx is fine but its setting the TUSER signal. I think this is because the packet length is less than some minimum value. But surely if its an ARP packet this is OK. Can someone explain what the issue is? Thanks

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richardhead
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Registered: ‎08-01-2012

Runt packets must be padded to make the frame a minimum of 64 bytes. Wireshark will remove the padding. https://www.microchip.com/forums/m493473.aspx

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dpaul24
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Registered: ‎08-07-2014

@beandigital,

Page 97 of the spec, 'User Error Indication' explains when TUSER can be asserted.

I am trying to simulate the Xilinx TEMAC. I am using the example design but I have modified the testbench to send an ARP packet.I have copied this from a Wireshark capture. The data that comes out of the MAC rx is fine but its setting the TUSER signal. I think this is because the packet length is less than some minimum value.

Do you mean to say you Rx frame is less than 64 Bytes?

How do you know TUSER is being asserted? Do you have an ILA built in?

If there ia an ILA working on the MAC Rx side, then you can modify the existing ILA to give you info on the Rx Statistics Vector signal. The bits of the Rx Statistics Vector will indicate Rx frame error if any.

In any case, a TEMAC simulation model is easy to set up and running. From the TB you can push in frames of your choice and observe the MAC Rx side for correctness.

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beandigital
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@dpaul24 

I am just using simulation and can see it set. I have increased the data payload to 46 bytes and I dont get the TUSER asserted now. Just curious why it would do this for an ARP packet. The wireshark packet didnt have 46 bytes.

Thanks

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dpaul24
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Registered: ‎08-07-2014

@beandigital,

Then I am interested in the structure of the ARP packet which you have copied from Wireshark.

Update.....

I see that ARP packet is 28 Bytes. Maybe that is the error cause.

The TEMAC core just conforms to the standard : Ethernet IEEE 802.3 standard defined the minimum Ethernet frame size as 64 bytes and the maximum as 1518 bytes.

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beandigital
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Registered: ‎04-27-2010
The Wireshark packet didnt have any padding unless it stripped it.
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richardhead
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Registered: ‎08-01-2012

Runt packets must be padded to make the frame a minimum of 64 bytes. Wireshark will remove the padding. https://www.microchip.com/forums/m493473.aspx

View solution in original post

beandigital
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Registered: ‎04-27-2010
Ok thanks for the info.
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