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2.11.3Receive Address Matching
The receive address block can store up to 32 addresses to be filtered or matched. Before enabling packet reception, all the address RAM locations should be initialized, including locations to be unused. The system software is responsible for adding and removing addresses from the RAM.
A MAC address location in RAM is 53 bits wide and consists of:
•48 bits of the MAC address.
•3 bits for the channel to which a valid address match will be transferred. The channel is a don’t care if MATCHFILT bit is cleared
•A valid bit
•A match or filter bit
First, write the index into the address RAM in the MACINDEX register to start writing a MAC address. Then write the upper 32 bits of the MAC address (MACADDRHI register), and then the lower 16 bits of MAC address with the VALID and MATCHFILT control bits (MACADDRLO). The valid bit should be cleared for the unused locations in the receive address RAM.
The most common uses for the receive address
•Set EMAC in promiscuous mode, using RXCAFEN and RXPROMCH bits in the RXMBPENABLE register. Then filter up to 32 individual addresses, which can be both unicast and/or multicast.
•Disable the promiscuous mode (RXCAFEN = 0) and match up to 32 individual addresses, multicast and/or unicast
2.11.4Hardware Receive QOS Support
Hardware receive quality of service (QOS) is supported, when enabled, by the Tag Protocol Identifier format and the associated Tag Control Information (TCI) format priority field. When the incoming frame length/type value is equal to 81.00h, the EMAC recognizes the frame as an Ethernet Encoded Tag Protocol Type. The two octets immediately following the protocol type contain the
•A
–The destination station'sindividual unicast address.
–The destination station'smulticast address (MACHASH1 and MACHASH2).
–The broadcast address of all ones.
•A
•The
•The
•Data bytes
•The 4 bytes CRC.
The receive filter low priority frame threshold register (RXFILTERLOWTHRESH) and the receive channel n free buffer count registers (RXnFREEBUFFER) are used in conjunction with the priority information to implement receive hardware QOS.
SPRUFI5B
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