Datasheet

____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
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Figure 10-10. TDM-over-Packet Encapsulation Formats
Table 10-6. Ethernet Frame Fields
Field Description
Preamble A sequence of 56 bits (alternating 1 and 0 values) Gives components in the network time to detect the
presence of a signal and synchronize to the incoming bit stream.
Start of Frame
Delimiter (SFD)
A sequence of 8 bits (10101011) that indicates the start of the frame.
Destination
Address and
Source Address
The Destination Address field identifies the station or stations that are to receive the frame. The Source
Address identifies the station that originated the frame. A Destination Address may specify either an
individual address destined for a single station, or a multicast address destined for a group of stations.
A Destination Address of all 1s refers to all stations on the LAN and is called the broadcast address.
Type Ethertype. The type of payload contained in the Ethernet frame.
Data and Padding This field contains the payload data transferred from the source station to the destination station(s). The
maximum size of this field is 1500 bytes. If the payload to be transported is less than 46 bytes, then
padding is used to bring the frame size up to the minimum length. A minimum-length Ethernet frame is
64 bytes from the Destination Address field through the Frame Check Sequence.
Frame Check
Sequence (FCS)
This field contains a 4-byte cyclical redundancy check (CRC) value used for error checking. When a
source station assembles a frame, it performs a CRC calculation on all the bits in the frame from the
Destination Address through the Pad fields (that is, all fields except the preamble, start frame delimiter,
and frame check sequence). The source station stores the calculated value in the FCS field and
transmits it as part of the frame. When the frame is received by the destination station, it performs an
identical check. If the calculated value does not match the value in the FCS field, the destination station
assumes an error has occurred during transmission and discards the frame.