Type: Answers

IP Product: Low Latency 10Gbps Ethernet MAC 1588 opt

Why do I see underflow errors when receiving Jumbo frames on the Low Latency Ethernet 10G MAC Design Examples?


Due to a problem with the design examples, the following design variants will see underflow errors when tested with packets that are more than 4100 bytes long:

1) 10M/100M/1G/10G Ethernet Design Example
2) 1G/10G Ethernet Design Example

This error is caused by the size of the external FIFO buffer between the MAC and traffic controller. The size, 8 x 512 bytes, is too small, causing the Avalon-ST valid signals to be de-asserted during the frame transmission.

Users will observe corrupted packets and CRC error reported by the packet monitor.


To work around this problem, increase the depth of the external FIFO, altera_eth_fifo_tx and altera_eth_fifo_rx instances, by changing the DC_FIFO_DEPTH & SC_FIFO_DEPTH parameter values from 512 to 2048 in rtl/altera_eth_channel.sv.