Fibre Channel Primer

27 Chapter 4: Physical and Signaling Layer
TRANSMISSION PROTOCOL: FC-1
The superior transmission characteristics of a dc-balanced
8B/10B code scheme are used at FC-1 for clock recovery, byte
synchronization, and encode/decode. This well-balanced code
developed by IBM allows for low-cost component design and provides
good transition density for easier clock recovery. A unique special
character, called a comma character, ensures proper byte and word
alignment. Other advantages of this code are its useful error detection
capability and a simple logic implementation for both encoder and
decoder. In this scheme, eight internal bits (one byte) are transmitted
as a 10-bit group. The block diagram in Figure 4.4 shows the 8B/10B
encoding scheme.
Figure 4.4 Superior transmission characteristics increase reliability
ABCDE FGHK
abcde i fghj
5B/6B
Functions
Byte
Clock
Parallel Data Byte
10 Bit Byte
to
Serializer on Media Interface Module
Control
3B/4B
Functions
Disparity
Control
A B C D E F G H K