Datasheet

Fibre Channel Interface
1-4 C141-C008
1.1.4 Port bypass circuit (BC)
Port bypass circuit is to bypass the drive if it cannot provide loop services.
For example, by removing the drive, unable to obtain valid data, or by any special
condition.
The port bypass circuit is located external to the drive. (for example, on the back
plane)
Figure 1.2 shows the relationship between the drive and the circuit.
Output
Input
Select
M
U
X
Drive
Port_A
Port_B
(2)
(1)
BC
From previous port
To next port
(1) Regular route (Bypass circuit off) (2) Via bypass (Bypass circuit on)
Figure 1.2 Port bypass circuit
1.1.5 Encoding & decoding
On FC-AL, the data is encoded prior to transmission and should be decoded when
receiving.
The 10-bit character consists of 1,024 data space with 13-bit data mapped 1
control character.
This method is called 8B/10B encoding.
And to prevent too many same signal (ones or zeros), 10-bit character has an
option to balance total numbers of ones or zeros.
This balancing is called “running disparity”.