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?

Description

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.

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

Workaround/Fix

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.