DS580 Datasheet, PDF (4/42 Pages) Xilinx, Inc – Optional MDIO interface for PHY access

LogiCORE IP XPS Ethernet Lite Media Access Controller
Start Frame Delimiter
The start frame delimiter field marks the start of the frame and must contain the pattern 10101011. The pattern is
transmitted from left to right. If a collision is detected during the transmission of the preamble or start of frame
delimiter fields, the transmission of both fields will be completed.
The receive data valid signal from the PHY (PHY_dv) may go active during the preamble but will be active prior to
the start frame delimiter field. For transmission, this field is always automatically inserted by the Ethernet Lite
MAC and should never appear in the packet data provided to the Ethernet Lite MAC. For reception, this field is
always stripped from the packet data.
Destination Address
The destination address field is 6 bytes in length⁽¹⁾. The least significant bit of the destination address is used to
determine if the address is an individual/unicast (0) or group/multicast (1) address. Multicast addresses are used
to group logically related stations.
The broadcast address (destination address field is all 1’s) is a multicast address that addresses all stations on the
LAN. The Ethernet Lite MAC supports transmission and reception of unicast and broadcast packets. The Ethernet
Lite MAC core does not support multicast packets.
This field is transmitted with the least significant bit first. This field is always provided in the packet data for trans-
missions and is always retained in the receive packet data.
Source Address
The source address field is 6 bytes in length⁽²⁾. This field is transmitted with the least significant bit first. This field
is always provided in the packet data for transmissions and is always retained in the receive packet data.
Type/Length
The type/length field is 2 bytes in length. When used as a length field, the value in this field represents the number
of bytes in the following data field. This value does not include any bytes that may have been inserted in the pad-
ding field following the data field.
The value of this field determines if it should be interpreted as a length as defined by the IEEE 802.3 standard or a
type field as defined by the ethernet protocol.
The maximum length of a data field is 1,500 bytes. Therefore, a value in this field that exceeds 1,500 (0x05DC) would
indicates that a frame type rather than a length value is provided in this field. The IEEE 802.3 standard uses the
value 1536 (0x0600) or greater to signal a type field.
The Ethernet Lite MAC does not perform any processing of the type/length field.
This field is transmitted with the least significant bit first but with the high order byte first. This field is always pro-
vided in the packet data for transmissions and is always retained in the receive packet data.
1. The Ethernet Lite MAC design does not support 16-bit destination addresses as defined in the IEEE 802 standard.
2. The Ethernet Lite MAC does not support 16-bit source addresses as defined in the IEEE 802 standard.
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DS580 September 21, 2010
Product Specification