Preamble (64 bits) (FDDI)

Protocol: FDDI FDDI PCI

Field: preamble

Length: 64 bits / 16 idle symbols

Contents: synchronization pattern.

FDDI stations need to synchronize with the signal's frequency; this is done by means of 64 preamble bits.

Token-Ring stations are always synchronous to received frames because there is always a signal passing the ring (idle symbols); they only need a 8-bit starting delimiter in order to get ready for receiving the frame.

The preamble is built up by idle symbols.