FCS - 9.0 English

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

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9.0 English

The value of the FCS field is calculated over the destination address, source address, length/type, data, and pad fields using a 32-bit Cyclic Redundancy Check (CRC) as defined in IEEE Std 802.3-2008 section 3.2.9:

G(x) = x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x1 + x0

The CRC bits are placed in the FCS field with the x31 term in the left-most bit of the first byte, and the x0 term is the rightmost bit of the last byte (that is, the bits of the CRC are transmitted in the order x31, x30,..., x1, x0 ).

For the transmission, this field can be inserted automatically by the Ethernet MAC or supplied by you, as indicated by a configuration register bit.

For reception, an incoming FCS value is verified on every frame. If an incorrect FCS value is received, the Ethernet MAC indicates that it has received a bad frame. The FCS field can either be passed on to you or be dropped by the Ethernet MAC, as indicated by a configuration register bit.