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AR# 45968

V6 TEMAC - Jumbo frame packet larger than 4K is truncated


When sending a jumbo frame packet larger than 4K, the data appears to be truncated at the MAC core.

I have turned on the "Jumbo frame" option in the Coregen options when I generated the core.


A jumbo frame is basically any frame that contains a payload of 1500 Bytes or larger. 

When sending jumbo frame packet, the length/ether type must be set correctly (0x8870).

The example design that is delivered along with the core has TX FIFO and RX FIFO to hold (buffer) the frame that is being sent or received. 

This example design FIFO is using a single RAMB36 primitive which is 36 bits including error correction (or effectively 4KB of data).

The MAC can handle larger frame packets as long as the length/ether field is set properly. 

If you are sending packets with a payload larger than 4KB, you must increase this FIFO size by instantiating another Block RAM and increasing the FIFO data width appropriately. 

The most significant bits will be connected to the enable pin of the Block RAMs to select the appropriate Block RAM depending on the address requested.

The FIFO is instantiated in client/fifo/*_fifo_8.v(hd)

Revision History:

1/23/2012 - Initial Release

AR# 45968
Date Created 01/23/2012
Last Updated 03/16/2015
Status Active
Type General Article
  • Tri-Mode Ethernet MAC