Visible to Intel only — GUID: nik1411172621489
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Visible to Intel only — GUID: nik1411172621489
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3.2.3.6. RX Automatic Pad Removal Control
In the 40GbE and 100GbE MAC configurations, you can enable and disable RX automatic pad removal with a configuration register bit in run-time.
The following figures illustrate the normal format of received data at the MAC RX interface.
In these figures, normal packet data, highlighted in gray, lasts until the end of the payload section. However, the IP core might pass along additional padding, marked with PAD, to ensure that the frame length is at least 64 bytes. The Ethernet standard requires padding insertion when the payload length is less than 46 bytes. EOP at the RX interface is normally marked after padding, but you can disable CRC removal to place the EOP at the end of the CRC block.
When enabled, RX automatic pad removal moves the EOP marker to the end of the payload as indicated in the length field, whether padding has been inserted or not. If the length is greater than 46 bytes, no padding has been inserted and this feature has no effect. When you enable RX automatic pad removal, the CRC is excluded from the EOP marker on packets that have stripped padding, and enabling CRC retention has no effect on padded packets.
The PAD_CONFIG register controls RX automatic pad removal. By default, pad removal is disabled. Statistics counting is not affected by RX automatic pad removal; data reports as default, as if the padding were not removed.