Fc-1 Features; Fc-1 And Initialization; 8B/10B Encoding And Decoding; Disparity - Sun Microsystems storagetek sl500 Reference Manual

FC-1 Features

FC-1 Features
The FC-1 level of the Fibre Channel protocol defines the transmission protocol.
This level includes the 8B/10B encoding/decoding scheme, word order
transmission, and error detection.

FC-1 and Initialization

During initialization, the FC-1 level provides an encoded bit stream (primitive
sequence) to the FC-0 level. When the FC-1 level, in turn, receives a proper bit
stream, the FC-1 level converts the stream into a form used by the FC-2 level. The
process achieves synchronization for both transmission characters and
transmission words.

8B/10B Encoding and Decoding

Fibre Channel uses a special process called encoding and decoding that is designed
to reduce distortion during transmission and aid in the detection of errors at the
receiving port. This process makes it highly likely that single and multiple bit
errors are detected.
Besides providing error detection, this process also balances the turning on and off
of the light for the loading of the optical fiber transmitters.
The process of encoding uses an algorithm that takes the original 8 bits in each byte
and transforms them into 10 bits for transmission. The result is an 8B/10B
encoding of a byte which is referred to as a transmission character.

Disparity

Along with the 8B/10B encoding, Fibre Channel uses another scheme to protect
transmission characters and aid in error detection: running disparity. Running
disparity adds a second dimension to the transmission of characters. This
dimension provides a balance of ones and zeros, which helps protect transmission
characters and controls the heat output of the transmitter.
A negative running disparity is maintained following the transmission of the end-
of-frame (EOF) delimiter. It remains negative until the transmission of the next
start-of-frame delimiter.
96122 • Revision: F Chapter 5 Fibre Channel Operations 45