Due to a problem in the Intel® Quartus® Prime Edition software version 18.1 and later, the 25G Ethernet Intel® FPGA IP core MAC frame length internal counter will overflow when frame length configuration register "MAX_TX_SIZE_CONFIG" and "MAX_RX_SIZE_CONFIG" is set to greater than 32k value.
Oversized frame error stays de-asserted as internal counter already overflow, hence not reflecting the actual error in hardware.
This problem is fixed starting from the Intel® Quartus® Prime Pro Edition v20.3 software onwards.
The 25G Ethernet Intel® FPGA IP core MAC design fixed detail as below:
- To handle frame length equal to MAX_TX_SIZE_CONFIG and MAX_RX_SIZE_CONFIG of 64k moving forwards.
- Also if Ethernet packet frames with a size larger than 64k is received in the 25G Ethernet Intel® FPGA IP core, the MAC will detect the overflow condition and stops incrementing the internal frame length counter. Oversized frame error will also get asserted to indicate an overflow scenario.