Why does the Low Latency 40-100 Gbps Ethernet IP core hang or send erroneous packets for certain TX Avalon-ST interface conditions?

The Low Latency 40-100 Gbps Ethernet IP core versions that predate the Quartus® Prime software v16.0 do not correctly handle the following conditions on the TX Avalon-ST interface. Any designs using the earlier versions of the IP core may hang or send erroneous packets if the below conditions occur:

1. TX valid goes low within a valid packet between Start-of-Packet (SOP) and End-of-Packet (EOP) (client resets the valid signal during transmission of a multi-cycle packet)
2. Packet size less than nine bytes
3. Back to back SOPs
4. Back to back EOPs

Although the Avalon-ST protocol allows these situations, the IP core does not support them.

Erroneous packets could have FCS or other errors, or could have less than the minimum IPG length.

In the pre-16.0 versions of the IP core, you must modify the application to avoid these conditions. The IP core hang issue is fixed in the Low Latency 40-100 Gbps Ethernet IP core v16.0 and later. The IP core identifies these conditions as invalid inputs and flags them as errors.