Preamble - 9.0 English

Tri-Mode Ethernet MAC LogiCORE IP Product Guide (PG051)

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9.0 English

For transmission, this field is automatically inserted by the Ethernet MAC. The preamble field was historically used for synchronization and contains seven bytes with the pattern 0x55 transmitted from left to right. For the reception, this field is always stripped from the incoming frame before the data is passed to you. The Ethernet MAC can receive Ethernet frames even if the preamble does not exist as long as a valid start of frame delimiter is available.